Guess the number/With feedback (player)

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Task
Guess the number/With feedback (player)
You are encouraged to solve this task according to the task description, using any language you may know.

The task is to write a player for the game that follows the following rules:

The scorer will choose a number between set limits. The computer player will print a guess of the target number. The computer asks for a score of whether its guess is higher than, lower than, or equal to the target. The computer guesses, and the scorer scores, in turn, until the computer correctly guesses the target number.

The computer should guess intelligently based on the accumulated scores given. One way is to use a Binary search based algorithm.

Cf.

Contents

[edit] Ada

with Ada.Text_IO;
procedure Guess_Number_Player is
procedure Guess_Number (Lower_Limit : Integer; Upper_Limit : Integer) is
type Feedback is (Lower, Higher, Correct);
package Feedback_IO is new Ada.Text_IO.Enumeration_IO (Feedback);
My_Guess : Integer := Lower_Limit + (Upper_Limit - Lower_Limit) / 2;
Your_Feedback : Feedback;
begin
Ada.Text_IO.Put_Line ("Think of a number!");
loop
Ada.Text_IO.Put_Line ("My guess: " & Integer'Image (My_Guess));
Ada.Text_IO.Put ("Your answer (lower, higher, correct): ");
Feedback_IO.Get (Your_Feedback);
exit when Your_Feedback = Correct;
if Your_Feedback = Lower then
My_Guess := Lower_Limit + (My_Guess - Lower_Limit) / 2;
else
My_Guess := My_Guess + (Upper_Limit - My_Guess) / 2;
end if;
end loop;
Ada.Text_IO.Put_Line ("I guessed well!");
end Guess_Number;
package Int_IO is new Ada.Text_IO.Integer_IO (Integer);
Lower_Limit : Integer;
Upper_Limit : Integer;
begin
loop
Ada.Text_IO.Put ("Lower Limit: ");
Int_IO.Get (Lower_Limit);
Ada.Text_IO.Put ("Upper Limit: ");
Int_IO.Get (Upper_Limit);
exit when Lower_Limit < Upper_Limit;
Ada.Text_IO.Put_Line ("Lower limit must be lower!");
end loop;
Guess_Number (Lower_Limit, Upper_Limit);
end Guess_Number_Player;

[edit] AutoHotkey

Works with the AutoHotkey entry at: Guess the number/With feedback

MaxGuesses = 50
 
GetParams(LowerBound,UpperBound)
If Not GuessNum(LowerBound,UpperBound,MaxGuesses)
MsgBox, 16, Error, Could not guess number within %MaxGuesses% guesses.
 
GetParams(ByRef LowerBound,ByRef UpperBound)
{
WinWait, Number Guessing ahk_class #32770
Sleep, 100
WinGet, InputID, ID
ControlGetText, Temp1, Static1, ahk_id %InputID%
Temp2 := InStr(Temp1,A_Space,False,32)
LowerBound := SubStr(Temp1,31,Temp2 - 31)
UpperBound := SubStr(Temp1,Temp2 + 5,-1)
}
 
GuessNum(LowerBound,UpperBound,MaxGuesses)
{
Loop, %MaxGuesses%
{
Guess := LowerBound + ((UpperBound - LowerBound) // 2)
Temp1 := SendGuess(Guess)
ToolTip % Temp1
If Temp1 = Too Low
LowerBound = %Guess%
Else If Temp1 = Too High
UpperBound = %Guess%
Else
Return, 1
}
}
 
SendGuess(Guess)
{
WinGet, InputID, ID, Number Guessing ahk_class #32770
ControlSetText, Edit1, %Guess%, ahk_id %InputID%
ControlSend, Button1, {Enter}, ahk_id %InputID%
Loop
{
Sleep, 50
IfWinExist, Correct ahk_class #32770
Return
Else IfWinExist, Incorrect ahk_class #32770
Break
}
ControlGetText, Temp1, Static2
WinClose
WinWaitClose
IfInString, Temp1, low
Return, "Too Low"
Else
Return, "Too High"
}

[edit] BBC BASIC

      min% = 1
max% = 100
PRINT "Think of a number between "; min% " and " ;max%
PRINT "I will try to guess your number."
REPEAT
guess% = (min% + max%) DIV 2
PRINT "My guess is " ; guess%
INPUT "Is it higher than, lower than or equal to your number", answer$
CASE LEFT$(answer$,1) OF
WHEN "L","l": min% = guess% + 1
WHEN "H","h": max% = guess% - 1
WHEN "E","e": EXIT REPEAT
OTHERWISE: PRINT "Sorry, I didn't understand your answer."
ENDCASE
UNTIL FALSE
PRINT "Goodbye."
END

[edit] C

#include <stdio.h>
 
int main(){
int bounds[ 2 ] = {1, 100};
char input[ 2 ] = " ";
/* second char is for the newline from hitting [return] */
int choice = (bounds[ 0 ] + bounds[ 1 ]) / 2;
/* using a binary search */
 
printf( "Choose a number between %d and %d.\n", bounds[ 0 ], bounds[ 1 ] );
 
do{
switch( input[ 0 ] ){
case 'H':
bounds[ 1 ] = choice;
break;
case 'L':
bounds[ 0 ] = choice;
break;
case 'Y':
printf( "\nAwwwright\n" );
return 0;
}
choice = (bounds[ 0 ] + bounds[ 1 ]) / 2;
 
printf( "Is the number %d? (Y/H/L) ", choice );
}while( scanf( "%1s", input ) == 1 );
 
return 0;
}

Demonstration (number is 57):

Choose a number between 1 and 100.
Is the number 50? (Y/H/L) L
Is the number 75? (Y/H/L) H
Is the number 62? (Y/H/L) H
Is the number 56? (Y/H/L) L
Is the number 59? (Y/H/L) H
Is the number 57? (Y/H/L) Y

Awwwright

The following is a hacky solution using bsearch() and pointers to represent integers. Although the pointers do not point to valid things, bsearch() doesn't actually dereference the pointers or care what they point to; it just passes them to the comparator and searches the space of pointers. We can use that to search any space of integers.

Translation of: Java
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
 
enum {
LOWER = 0,
UPPER = 100,
KEY = LOWER-1 // some value that is not in the valid range
};
 
char dummy;
// A pointer to represent the integer 0, and the basis of our integer-as-pointer
// representation. We can't use the null pointer because bsearch() returns that
// for not found.
#define ZERO ((void *)&dummy)
 
int get_value(int x) {
if (x == KEY)
return 0;
printf("My guess is: %d. Is it too high, too low, or correct? (H/L/C) ", x);
char input[2] = " ";
scanf("%1s", input);
switch (tolower(input[0])) {
case 'l':
return -1;
case 'h':
return 1;
case 'c':
return 0;
}
fprintf(stderr, "Invalid input\n");
exit(1);
return 0;
}
 
int my_cmp(const void *x, const void *y) {
return get_value(x - ZERO) - get_value(y - ZERO);
}
 
int main() {
printf("Instructions:\n"
"Think of integer number from %d (inclusive) to %d (exclusive) and\n"
"I will guess it. After each guess, you respond with L, H, or C depending\n"
"on if my guess was too low, too high, or correct.\n",
LOWER, UPPER);
void *result = bsearch(ZERO + KEY, ZERO + LOWER, UPPER-LOWER, 1, my_cmp);
if (result == NULL)
fprintf(stderr, "That is impossible.\n");
else
printf("Your number is %d.\n", (int)(result - ZERO));
return 0;
}

[edit] C++

A clever solution that takes advantage of C++'s built-in binary search function lower_bound(). Instead of searching a slice of a container, we search a range of numbers by implementing a specially-designed custom iterator.

Translation of: Go
#include <iostream>
#include <algorithm>
#include <string>
#include <iterator>
 
struct GuessNumberIterator : std::iterator<std::random_access_iterator_tag, int> {
int i;
GuessNumberIterator() { }
GuessNumberIterator(int _i) : i(_i) { }
GuessNumberIterator& operator++() { ++i; return *this; }
GuessNumberIterator operator++(int) {
GuessNumberIterator tmp = *this; ++(*this); return tmp; }
bool operator==(const GuessNumberIterator& y) { return i == y.i; }
bool operator!=(const GuessNumberIterator& y) { return i != y.i; }
int operator*() {
std::cout << "Is your number less than or equal to " << i << "? ";
std::string s;
std::cin >> s;
return (s != "" && (s[0] == 'y' || s[0] == 'Y')) ? 0 : -1;
}
GuessNumberIterator& operator--() { --i; return *this; }
GuessNumberIterator operator--(int) {
GuessNumberIterator tmp = *this; --(*this); return tmp; }
GuessNumberIterator& operator+=(int n) { i += n; return *this; }
GuessNumberIterator& operator-=(int n) { i -= n; return *this; }
GuessNumberIterator operator+(int n) {
GuessNumberIterator tmp = *this; return tmp += n; }
GuessNumberIterator operator-(int n) {
GuessNumberIterator tmp = *this; return tmp -= n; }
int operator-(const GuessNumberIterator &y) { return i - y.i; }
int operator[](int n) { return *(*this + n); }
bool operator<(const GuessNumberIterator &y) { return i < y.i; }
bool operator>(const GuessNumberIterator &y) { return i > y.i; }
bool operator<=(const GuessNumberIterator &y) { return i <= y.i; }
bool operator>=(const GuessNumberIterator &y) { return i >= y.i; }
};
inline GuessNumberIterator operator+(int n, GuessNumberIterator &i) { return i + n; }
 
const int lower = 0;
const int upper = 100;
 
int main() {
std::cout << "Instructions:\n"
<< "Think of integer number from " << lower << " (inclusive) to "
<< upper << " (exclusive) and\n"
<< "I will guess it. After each guess, I will ask you if it is less than\n"
<< "or equal to some number, and you will respond with \"yes\" or \"no\".\n";
int answer = std::lower_bound(GuessNumberIterator(lower), GuessNumberIterator(upper), 0).i;
std::cout << "Your number is " << answer << ".\n";
return 0;
}

[edit] C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading; //Remember to add this if you want the game to pause in RealisticGuess.Start()
 
namespace ConsoleApplication1
{
class RealisticGuess //Simulates a guessing game between two people. Guessing efficiency is not a goal.
{
private int max;
private int min;
private int guess;
 
public void Start()
{
Console.Clear();
string input;
 
try
{
Console.WriteLine("Please enter the lower boundary");
input = Console.ReadLine();
min = Convert.ToInt32(input);
Console.WriteLine("Please enter the upper boundary");
input = Console.ReadLine();
max = Convert.ToInt32(input);
}
catch (FormatException)
{
Console.WriteLine("The entry you have made is invalid. Please make sure your entry is an integer and try again.");
Console.ReadKey(true);
Start();
}
Console.WriteLine("Think of a number between {0} and {1}.", min, max);
Thread.Sleep(2500);
Console.WriteLine("Ready?");
Console.WriteLine("Press any key to begin.");
Console.ReadKey(true);
Guess(min, max);
}
public void Guess(int min, int max)
{
int counter = 1;
string userAnswer;
bool correct = false;
Random rand = new Random();
 
while (correct == false)
{
guess = rand.Next(min, max);
Console.Clear();
Console.WriteLine("{0}", guess);
Console.WriteLine("Is this number correct? {Y/N}");
userAnswer = Console.ReadLine();
if (userAnswer != "y" && userAnswer != "Y" && userAnswer != "n" && userAnswer != "N")
{
Console.WriteLine("Your entry is invalid. Please enter either 'Y' or 'N'");
Console.WriteLine("Is the number correct? {Y/N}");
userAnswer = Console.ReadLine();
}
if (userAnswer == "y" || userAnswer == "Y")
{
correct = true;
}
if (userAnswer == "n" || userAnswer == "N")
{
counter++;
if (max == min)
{
Console.WriteLine("Error: Range Intersect. Press enter to restart the game."); //This message should never pop up if the user enters good data.
Console.ReadKey(true); //It handles the game-breaking exception that occurs
Guess(1, 101); //when the max guess number is the same as the min number.
}
Console.WriteLine("Is the number you're thinking of lower or higher? {L/H}");
userAnswer = Console.ReadLine();
if (userAnswer != "l" && userAnswer != "L" && userAnswer != "h" && userAnswer != "H")
{
Console.WriteLine("Your entry is invalid. Please enter either 'L' or 'H'");
Console.WriteLine("Is the number you're thinking of lower or higher? {L/H}");
userAnswer = Console.ReadLine();
}
if (userAnswer == "l" || userAnswer == "L")
{
max = guess;
}
if (userAnswer == "h" || userAnswer == "H")
{
min = guess;
}
}
}
if (correct == true)
{
EndAndLoop(counter);
}
}
 
public void EndAndLoop(int iterations)
{
string userChoice;
bool loop = false;
Console.WriteLine("Game over. It took {0} guesses to find the number.", iterations);
while (loop == false)
{
Console.WriteLine("Would you like to play again? {Y/N}");
userChoice = Console.ReadLine();
if (userChoice != "Y" && userChoice != "y" && userChoice != "N" && userChoice != "n")
{
Console.WriteLine("Sorry, your input is invalid. Please answer 'Y' to play again, or 'N' to quit.");
}
if (userChoice == "Y" || userChoice == "y")
{
Start();
}
if (userChoice == "N" || userChoice == "n")
{
Environment.Exit(1);
}
}
}
}
class Program
{
static void Main(string[] args)
{
Console.Title = "Random Number";
RealisticGuess game = new RealisticGuess();
game.Start();
}
}
}
 

[edit] Clojure

(require '[clojure.string :as str])
 
(defn guess-game [low high]
(printf "Think of a number between %s and %s.\n (use (h)igh (l)ow (c)orrect)\n" low high)
(loop [guess (/ (inc (- high low)) 2)
[step & more] (next (iterate #(/ % 2) guess))]
(printf "I guess %s\n=> " (Math/round (float guess)))
(flush)
(case (first (str/lower-case (read)))
\h (recur (- guess step) more)
\l (recur (+ guess step) more)
\c (println "Huzzah!")
(do (println "Invalid input.")
(recur guess step)))))

Output

user=> (guess-game 1 100)
Think of a number between 1 and 100.
 (use (h)igh (l)ow (c)orrect)
I guess 50
=> l
I guess 63
=> h
I guess 56
=> l
I guess 59
=> l
I guess 61
=> c
Huzzah!

[edit] D

Translation of: Python
import std.stdio, std.string;
 
void main() {
immutable mnOrig = 1, mxOrig = 10;
int mn = mnOrig, mx = mxOrig;
 
writefln(
"Think of a number between %d and %d and wait for me to guess it.
On every guess of mine you should state whether the guess was
too high, too low, or equal to your number by typing h, l, or ="
,
mn, mx);
 
LOOP: for (int i = 1; ; i++) {
immutable guess = (mn + mx) / 2;
writef("Guess %2d is: %2d. The score for which is (h,l,=): ",
i, guess);
immutable string txt = readln().strip().toLower();
 
switch (txt) {
case "h":
mx = guess - 1;
break;
case "l":
mn = guess + 1;
break;
case "=":
writeln(" Yeehaw!!");
break LOOP;
default:
writefln(" I don't understand your input '%s'.",
txt);
continue LOOP;
}
 
if (mn > mx || mn < mnOrig || mx > mxOrig) {
writeln("Please check your scoring as" ~
" I cannot find the value");
break;
}
}
writeln("\nThanks for keeping score.");
}
Output:
Think of a number between 1 and 10 and wait for me to guess it.
    On every guess of mine you should state whether the guess was
    too high, too low, or equal to your number by typing h, l, or =
Guess  1 is:  5. The score for which is (h,l,=): l
Guess  2 is:  8. The score for which is (h,l,=): h
Guess  3 is:  6. The score for which is (h,l,=): l
Guess  4 is:  7. The score for which is (h,l,=): =
  Yeehaw!!

Thanks for keeping score.

[edit] Erlang

% Implemented by Arjun Sunel
-module(guess_game).
-export([main/0]).
 
main() ->
L = 1 , % Lower Limit
U = 100, % Upper Limit
 
io:fwrite("Player 1 : Guess my number between ~p and ", [L]),
io:fwrite("and ~p until you get it right.\n", [U]),
N = random:uniform(100),
guess(L,U,N).
 
guess(L,U,N) ->
K = (L+U) div 2,
io:format("Player 2 : Number guessed : ~p~n",[K]),
if
K=:=N ->
io:format("Well guessed!! by Player 2\n");
true ->
if
K > N ->
io:format("Player 1 : Your guess is too high!\n"),
guess(L,K,N);
true ->
io:format("Player 1 : Your guess is too low!\n"),
guess(K,U,N)
end
end.
Output:
Player 1 : Guess my number between 1 and and 100 until you get it right.
Player 2 : Number guessed : 50
Player 1 : Your guess is too high!
Player 2 : Number guessed : 25
Player 1 : Your guess is too high!
Player 2 : Number guessed : 13
Player 1 : Your guess is too high!
Player 2 : Number guessed : 7
Player 1 : Your guess is too low!
Player 2 : Number guessed : 10
Well guessed!! by Player 2
ok

[edit] Euphoria

Translation of: PureBasic
include get.e
include wildcard.e
 
sequence Respons
integer min, max, Guess
min = 0
max = 100
 
printf(1,"Think of a number between %d and %d.\n",{min,max})
puts(1,"On every guess of mine you should state whether my guess was\n")
puts(1,"too high, too low, or equal to your number by typing 'h', 'l', or '='\n")
 
while 1 do
if max < min then
puts(1,"I think something is strange here...\n")
exit
end if
Guess = floor((max-min)/2+min)
printf(1,"My guess is %d, is this correct? ", Guess)
Respons = upper(prompt_string(""))
if Respons[1] = 'H' then
max = Guess-1
elsif Respons[1] = 'L' then
min = Guess+1
elsif Respons[1] = '=' then
puts(1,"I did it!\n")
exit
else
puts(1,"I do not understand that...\n")
end if
end while

[edit] Fantom

 
class Main
{
public static Void main ()
{
Int lowerLimit := 1
Int higherLimit := 100
 
echo ("Think of a number between 1 and 100")
echo ("Press 'enter' when ready")
Env.cur.in.readLine
 
while (true)
{
if (higherLimit < lowerLimit)
{ // check that player is not cheating!
echo ("Something has gone wrong ... I give up")
break
}
myGuess := (higherLimit + lowerLimit) / 2
echo ("My guess is $myGuess")
echo ("Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal")
switch (Env.cur.in.readLine.trim.upper)
{
case "E":
echo ("I got it correct - thankyou!")
break // game over
case "H":
lowerLimit = myGuess + 1
case "L":
higherLimit = myGuess - 1
default:
echo ("Pardon? Let's try that again")
}
}
}
}
 

Example:

Think of a number between 1 and 100
Press 'enter' when ready

My guess is 50
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
a
Pardon? Let's try that again
My guess is 50
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
l
My guess is 25
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
h
My guess is 37
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
h
My guess is 43
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
h
My guess is 46
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
h
My guess is 48
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
l
My guess is 47
Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal
e
I got it correct - thankyou!

[edit] Fortran

Works with: Fortran version 95 and later
program Guess_a_number_Player
implicit none
 
integer, parameter :: limit = 100
integer :: guess, mx = limit, mn = 1
real :: rnum
character(1) :: score
 
write(*, "(a, i0, a)") "Think of a number between 1 and ", limit, &
" and I will try to guess it."
write(*, "(a)") "You score my guess by entering: h if my guess is higher than that number"
write(*, "(a)") " l if my guess is lower than that number"
write(*, "(a/)") " c if my guess is the same as that number"
 
call random_seed
call random_number(rnum)
guess = rnum * limit + 1
do
write(*, "(a, i0, a,)", advance='no') "My quess is: ", guess, " Score(h, l or c)?: "
read*, score
select case(score)
case("l", "L")
mn = guess
guess = (mx-guess+1) / 2 + mn
 
case("h", "H")
mx = guess
guess = mx - (guess-mn+1) / 2
 
case("c", "C")
write(*, "(a)") "I solved it!"
exit
 
case default
write(*, "(a)") "I did not understand that"
end select
end do
end program

Output

Think of a number between 1 and 100 and I will try to guess it.
You score my guess by entering: h if my guess is higher than that number
                                l if my guess is lower than that number
                                c if my guess is the same as that number

My guess is: 58   Score(h, l or c)?: h
My guess is: 29   Score(h, l or c)?: l
My guess is: 44   Score(h, l or c)?: l 
My guess is: 51   Score(h, l or c)?: l 
My guess is: 55   Score(h, l or c)?: l 
My guess is: 57   Score(h, l or c)?: c
I solved it!

[edit] Go

Go's binary search function (sort.Search()) is general enough to be able to do this type of task, as mentioned in the documentation for the function itself.[1]

package main
 
import (
"fmt"
"sort"
)
 
func main() {
lower, upper := 0, 100
fmt.Printf(`Instructions:
Think of integer number from %d (inclusive) to %d (exclusive) and
I will guess it. After each guess, I will ask you if it is less than
or equal to some number, and you will respond with "yes" or "no".
`
, lower, upper)
answer := sort.Search(upper-lower, func (i int) bool {
fmt.Printf("Is your number less than or equal to %d? ", lower+i)
s := ""
fmt.Scanf("%s", &s)
return s != "" && s[0] == 'y'
})
fmt.Printf("Your number is %d.\n", lower+answer)
}

Manual solution:

package main
 
import (
"bufio"
"fmt"
"os"
)
 
func main() {
lower, upper := 1, 100
fmt.Printf(`Instructions:
Think of integer number from %d (inclusive) to %d (inclusive) and I will guess it.
After each guess, you respond with l,h,or c depending on
if my guess was too low, too high, or correct.
Press enter when you are thinking of a number. `
, lower, upper)
in := bufio.NewReader(os.Stdin)
in.ReadString('\n')
for {
guess := (upper+lower)/2
fmt.Printf("My guess: %d (l/h/c) ", guess)
s, err := in.ReadString('\n')
if err != nil {
fmt.Println("\nSo, bye.")
return
}
switch s {
case "l\n":
lower = guess + 1
case "h\n":
upper = guess - 1
case "c\n":
fmt.Println("I did it. :)")
return
default:
fmt.Println("Please respond by pressing l, h, or c")
}
}
}

[edit] Icon and Unicon

Translation of: Fantom
 
procedure main ()
lower_limit := 1
higher_limit := 100
 
write ("Think of a number between 1 and 100")
write ("Press 'enter' when ready")
read ()
 
repeat {
if (higher_limit < lower_limit)
then { # check that player is not cheating!
write ("Something has gone wrong ... I give up")
exit ()
}
my_guess := (higher_limit + lower_limit) / 2
write ("My guess is ", my_guess)
write ("Enter 'H' if your number is higher, 'L' if lower, or 'E' if equal")
reply := map(trim(read ()))
case (reply) of {
"e" : {
write ("I got it correct - thankyou!")
exit () # game over
}
"h" : lower_limit := my_guess + 1
"l" : higher_limit := my_guess - 1
default : write ("Pardon? Let's try that again")
}
}
end
 

[edit] J

require 'misc'
guess=:3 :0
'lo hi'=.y
while.lo < hi do.
smoutput 'guessing a number between ',(":lo),' and ',":hi
guess=.lo+?hi-lo
select.{.deb tolower prompt 'is it ',(":guess),'? '
case.'y'do. smoutput 'Win!' return.
case.'l'do. lo=.guess+1
case.'h'do. hi=.guess-1
case.'q'do. smoutput 'giving up' return.
case. do. smouput 'options: yes, low, high, quit'
end.
end.
)

Example session:

   guess 1 100
guessing a number between 1 and 100
is it 86? hi
guessing a number between 1 and 85
is it 56? hi
guessing a number between 1 and 55
is it 24? lo
guessing a number between 25 and 55
is it 29? lo
guessing a number between 30 and 55
is it 43? lo
guessing a number between 44 and 55
is it 53? hi
guessing a number between 44 and 52
is it 51? hi
guessing a number between 44 and 50
is it 48? lo
guessing a number between 49 and 50
is it 49? lo
50

This could be made more efficient by replacing guess=.lo+?hi-lo with guess=.<.-:lo+hi. (The above example would have finished on the first guess, but the range 1..100 would never take more than 6 guesses -- the remaining answers would be determined after six guesses.)

[edit] Java

A clever solution that uses the built-in binary search functions with a virtual list.

Translation of: Go
import java.util.AbstractList;
import java.util.Collections;
import java.util.Scanner;
 
public class GuessNumber {
public static final int LOWER = 0, UPPER = 100;
public static void main(String[] args) {
System.out.printf("Instructions:\n" +
"Think of integer number from %d (inclusive) to %d (exclusive) and\n" +
"I will guess it. After each guess, you respond with L, H, or C depending\n" +
"on if my guess was too low, too high, or correct.\n",
LOWER, UPPER);
int result = Collections.binarySearch(new AbstractList<Integer>() {
private final Scanner in = new Scanner(System.in);
public int size() { return UPPER - LOWER; }
public Integer get(int i) {
System.out.printf("My guess is: %d. Is it too high, too low, or correct? (H/L/C) ", LOWER+i);
String s = in.nextLine();
assert s.length() > 0;
switch (Character.toLowerCase(s.charAt(0))) {
case 'l':
return -1;
case 'h':
return 1;
case 'c':
return 0;
}
return -1;
}
}, 0);
if (result < 0)
System.out.println("That is impossible.");
else
System.out.printf("Your number is %d.\n", result);
}
}

[edit] JavaScript

[edit] Spidermonkey version

A boring solution that does nothing clever or inscrutable.

Well, it does use recursion for the guessing function, but that's OK because the depth is bounded by LOG2 of the range. That's not true if the user changes his number, but then he gets what he deserves.

#!/usr/bin/env js
 
var DONE = RIGHT = 0, HIGH = 1, LOW = -1;
 
function main() {
showInstructions();
while (guess(1, 100) !== DONE);
}
 
function guess(low, high) {
if (low > high) {
print("I can't guess it. Perhaps you changed your number.");
return DONE;
}
 
var g = Math.floor((low + high) / 2);
var result = getResult(g);
switch (result) {
case RIGHT:
return DONE;
case LOW:
return guess(g + 1, high);
case HIGH:
return guess(low, g - 1);
}
}
 
function getResult(g) {
while(true) {
putstr('Is it ' + g + '? ');
var ans = readline().toUpperCase().replace(/^\s+/, '') + ' ';
switch (ans[0]) {
case 'R':
print('I got it! Thanks for the game.');
return RIGHT;
case 'L':
return LOW;
case 'H':
return HIGH;
default:
print('Please tell me if I am "high", "low" or "right".');
}
}
}
 
function showInstructions() {
print('Think of a number between 1 and 100 and I will try to guess it.');
print('After I guess, type "low", "high" or "right", and then press enter.');
putstr("When you've thought of a number press enter.");
readline();
}
 
main();
 

An example session:

Think of a number between 1 and 100 and I will try to guess it.
After I guess, type "low", "high" or "right", and then press enter.
When you've thought of a number press enter.
Is it 50? high
Is it 25? high
Is it 12? low
Is it 18? high
Is it 15? high
Is it 13? right
I got it! Thanks for the game.

Another example session:

Think of a number between 1 and 100 and I will try to guess it.
After I guess, type "low", "high" or "right", and then press enter.
When you've thought of a number press enter.
Is it 50? n
Please tell me if I am "high", "low" or "right".
Is it 50? h
Is it 25? h
Is it 12? h
Is it 6? h
Is it 3? h
Is it 1? h
I can't guess it. Perhaps you changed your number.


[edit] Lasso

#!/usr/bin/lasso9
 
local(
mini=0,
maxi=100,
status = false,
count = 0,
response,
guess
)
 
stdoutnl('Think of a number between ' + #mini + ' and ' + #maxi + '
Each time I guess indicate if I was to high (H), to low (L) or just right (R).')
 
 
while(not #status) => {
 
if(not(#mini <= #maxi)) => {
 
stdout('I think you are trying to cheat me. I will not play anymore.')
#status = true
 
else
 
#guess = ((#maxi - #mini) /2 ) + #mini
 
stdout('You are thinking on ' + #guess + ' ')
#response = null
 
// the following bits wait until the terminal gives you back a line of input
while(not #response or #response -> size == 0) => {
#response = file_stdin -> readSomeBytes(1024, 1000)
}
#response -> replace(bytes('\n'), bytes(''))
 
match(string(#response)) => {
case('L')
#mini = #guess + 1
#count++
case('H')
#maxi = #guess - 1
#count++
case('R')
stdout('Am I smart or smart! I guessed it in ' + #count ' tries!')
#status = true
case()
stdout('Are you having issues reading instructions? ')
}
}
}

Examples:

Think of a number between 0 and 100
Each time I guess indicate if I was to high (H), to low (L) or just right (R).
You are thinking on 50 l
You are thinking on 75 l
You are thinking on 88 h
You are thinking on 81 r
Am I smart or smart! I guessed it in 4 tries!
Think of a number between 0 and 100
Each time I guess indicate if I was to high (H), to low (L) or just right (R).
You are thinking on 50 k
Are you having issues reading instructions? You are thinking on 50 tr
Are you having issues reading instructions? You are thinking on 50 l
You are thinking on 75 l
You are thinking on 88 l
You are thinking on 94 l
You are thinking on 97 l
You are thinking on 99 h
You are thinking on 98 r
Am I smart or smart! I guessed it in 6 tries!
You are thinking on 50 h
You are thinking on 24 h
You are thinking on 11 l
You are thinking on 17 l
You are thinking on 20 l
You are thinking on 22 l
You are thinking on 23 l
I think you are trying to cheat me. I will not play anymore.

[edit] Liberty BASIC

mini=0
maxi=100
 
print "Think of a number between ";mini;" and ";maxi
print "Each time I guess a number you must state whether my"
print "guess was too high, too low, or equal to your number."
print
 
while response$<>"="
if not(mini<=maxi) then
print "Error"
exit while
end if
guess=int((maxi-mini)/2)+mini
print "My guess is ";guess;". Type L for low, H for high, = for correct."
input response$
response$=upper$(response$)
select case response$
case "L"
mini=guess+1
case "H"
maxi=guess-1
case "="
print guess;" is correct."
exit while
case else
print "Your response was not helpful."
end select
wend
print "Thanks for playing."

[edit] Lua

function wait(waittime)--wait function is used so that app will not quit immediately
local timer = os.time()
repeat until os.time() == timer + waittime
end
 
 
upperBound = 100
lowerBound = 0
print("Think of an integer between 1 to 100.")
print("I will try to guess it.")
while true do
upper1 = upperBound+1
upper2 = upperBound-1
if upperBound == lowerBound or upper1 == lowerBound or upper2 == lowerBound or lowerBound > upperBound then--make sure player is not cheating
io.write("You're cheating! I'm not playing anymore. Goodbye.")
wait(3)
break
else
Guess = math.floor((upperBound + lowerBound)/2)--guessing mechanism
print("My guess is: "..Guess..". Is it too high, too low, or correct? (h/l/c)")
input = io.read()
 
if input == "h" then --higher
upperBound = Guess
elseif input == "l" then --lower
lowerBound = Guess
elseif input == "c" then --correct
io.write("So I win? Thanks for playing with me.")
wait(3)
break
else
print("Invalid input. Please try again. ")
end
end
end
 

[edit] MATLAB

function GuessNumberFeedbackPlayer
 
lowVal = input('Lower limit: ');
highVal = input('Upper limit: ');
fprintf('Think of your number. Press Enter when ready.\n')
pause
nGuesses = 1;
done = false;
while ~done
guess = floor(0.5*(lowVal+highVal));
score = input(sprintf( ...
'Is %d too high (H), too low (L), or equal (E)? ', guess), 's');
if any(strcmpi(score, {'h' 'hi' 'high' 'too high' '+'}))
highVal = guess-1;
nGuesses = nGuesses+1;
elseif any(strcmpi(score, {'l' 'lo' 'low' 'too low' '-'}))
lowVal = guess+1;
nGuesses = nGuesses+1;
elseif any(strcmpi(score, {'e' 'eq' 'equal' 'right' 'correct' '='}))
fprintf('Yay! I win in %d guesses.\n', nGuesses)
done = true;
else
fprintf('Unclear response. Try again.\n')
end
if highVal < lowVal
fprintf('Incorrect scoring. No further guesses.\n')
done = true;
end
end
end
Output:
Lower limit: 0
Upper limit: 50
Think of your number. Press Enter when ready.
Is 25 too high (H), too low (L), or equal (E)? L
Is 38 too high (H), too low (L), or equal (E)? H
Is 31 too high (H), too low (L), or equal (E)? H
Is 28 too high (H), too low (L), or equal (E)? L
Is 29 too high (H), too low (L), or equal (E)? E
Yay! I win in 5 guesses.
Lower limit: 0
Upper limit: 10
Think of your number. Press Enter when ready.
Is 5 too high (H), too low (L), or equal (E)? L
Is 8 too high (H), too low (L), or equal (E)? hello
Unclear response. Try again.
Is 8 too high (H), too low (L), or equal (E)? H
Is 6 too high (H), too low (L), or equal (E)? L
Is 7 too high (H), too low (L), or equal (E)? H
Incorrect scoring. No further guesses.

[edit] Mathematica

guessnumber[min0_, max0_] := 
DynamicModule[{min = min0, max = max0, guess, correct = False},
guess[] := Round@Mean@{min, max};
Dynamic@If[correct, Row@{"Your number is ", guess[], "."},
Column@{Row@{"I guess ", guess[], "."},
Row@{Button["too high", max = guess[]],
Button["too low", min = guess[]],
Button["correct", correct = True]}}]];
guessnumber[1, 100]

[edit] Modula-2

MODULE raden;
 
IMPORT InOut;
 
VAR done, ok : BOOLEAN;
guess, upp, low : CARDINAL;
res : CHAR;
 
BEGIN
InOut.WriteString ("Choose a number between 0 and 1000.");
InOut.WriteLn;
InOut.WriteLn;
upp := 1000;
low := 0;
REPEAT
ok := FALSE;
guess := ( ( upp - low ) DIV 2 ) + low;
InOut.WriteString ("My guess is"); InOut.WriteCard (guess, 4); InOut.Write (11C);
InOut.WriteString ("How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : ");
InOut.WriteBf;
REPEAT
InOut.Read (res);
res := CAP (res)
UNTIL (res = 'Q') OR (res = 'L') OR (res = 'H');
CASE res OF
'L' : low := guess |
'H' : upp := guess
ELSE
ok := TRUE
END;
UNTIL ok;
InOut.WriteString ("So the number is"); InOut.WriteCard (guess, 4);
InOut.WriteLn;
InOut.WriteString ("Thanks for letting me play with you.");
InOut.WriteLn
END raden.
Example:
raden

Choose a number between 0 and 1000.

My guess is 500 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : l My guess is 750 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : h My guess is 625 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : h My guess is 562 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : l My guess is 593 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : l My guess is 609 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : h My guess is 601 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : h My guess is 597 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : l My guess is 599 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : l My guess is 600 How did I score? 'L' = too low, 'H' = too high, 'Q' = OK : q So the number is 600

Thanks for letting me play with you.

[edit] Nimrod

import rdstdin, strutils
 
let oRange = 1..10
var iRange = oRange
 
echo """Think of a number between $# and $# and wait for me to guess it.
On every guess of mine you should state whether the guess was
too high, too low, or equal to your number by typing h, l, or =""".format(iRange.a, iRange.b)
 
var i = 0
while true:
inc i
let guess = (iRange.a + iRange.b) div 2
let txt = readLineFromStdin("Guess $# is: $#. The score for which is (h,l,=): "
.format(i, guess))
 
case txt
of "h": iRange.b = guess - 1
of "l": iRange.a = guess + 1
of "=":
echo " Ye-Haw!!"
break
else: echo " I don't understand your input of '%s'?".format(txt)
 
if iRange.a > iRange.b or iRange.a < oRange.a or iRange.b > oRange.b:
echo "Please check your scoring as I cannot find the value"
break
 
echo "Thanks for keeping score."

Output:

Think of a number between 1 and 10 and wait for me to guess it.
On every guess of mine you should state whether the guess was
too high, too low, or equal to your number by typing h, l, or =
Guess 1 is: 5. The score for which is (h,l,=): l
Guess 2 is: 8. The score for which is (h,l,=): h
Guess 3 is: 6. The score for which is (h,l,=): l
Guess 4 is: 7. The score for which is (h,l,=): =
  Ye-Haw!!
Thanks for keeping score.

[edit] Objective-C

A clever solution that uses the built-in binary search functions with a virtual list.

Translation of: Java
#import <Foundation/Foundation.h>
 
@interface GuessNumberFakeArray : NSArray {
int lower, upper;
}
- (instancetype)initWithLower:(int)l andUpper:(int)u;
@end
 
@implementation GuessNumberFakeArray
- (instancetype)initWithLower:(int)l andUpper:(int)u {
if ((self = [super init])) {
lower = l;
upper = u;
}
return self;
}
- (NSUInteger)count { return upper-lower; }
- (id)objectAtIndex:(NSUInteger)i {
printf("My guess is: %d. Is it too high, too low, or correct? (H/L/C) ", lower + (int)i);
char input[2] = " ";
scanf("%1s", input);
switch (tolower(input[0])) {
case 'l':
return @-1;
case 'h':
return @1;
case 'c':
return @0;
}
return nil;
}
@end
 
#define LOWER 0
#define UPPER 100
 
int main(int argc, const char *argv[]) {
@autoreleasepool {
 
printf("Instructions:\n"
"Think of integer number from %d (inclusive) to %d (exclusive) and\n"
"I will guess it. After each guess, you respond with L, H, or C depending\n"
"on if my guess was too low, too high, or correct.\n",
LOWER, UPPER);
NSUInteger result = [[[GuessNumberFakeArray alloc] initWithLower:LOWER andUpper:UPPER]
indexOfObject:[NSNumber numberWithInt: 0]
inSortedRange:NSMakeRange(0, UPPER - LOWER)
options:0
usingComparator:^(id x, id y){ return [x compare: y]; }];
if (result == NSNotFound)
printf("That is impossible.\n");
else
printf("Your number is %d.", LOWER + (int)result);
 
}
return 0;
}

[edit] PARI/GP

 
guessnumber2(b)={
my(c=0,d=b,a=0);
for(x=1,b,
for(y=1,b,
if(a<c||a==c||a==d||a>d,
a=random(b),
break()
)
);
print("I guess "a" am I h,l,or e ?");
g=input();
if(g==h,
d=a,
if(g==l,
c=a,
if(g==e,
break()
)
)
)
);
}
 

[edit] Pascal

Program GuessIt(input, output);
 
var
done, ok: boolean;
guess, upp, low: integer;
res: char;
 
begin
writeln ('Choose a number between 0 and 1000.');
write ('Press Enter and I will start to guess the number.');
readln;
upp := 1000;
low := 0;
repeat
ok := false;
guess := ( ( upp - low ) div 2 ) + low;
write ('My guess is: ', guess:4);
write ('. How did i score? ''l'' = too low, ''h'' = too high, ''c'' = correct : ');
repeat
readln (res);
res := lowercase(res);
until (res = 'c') or (res = 'l') or (res = 'h');
case res of
'l': low := guess;
'h': upp := guess;
else
ok := true
end;
until ok;
writeln ('So the number is: ', guess:4);
writeln ('It was nice to play with you.');
end.

Output:

:> ./GuessTheNumberPlayerFeedback
Choose a number between 0 and 1000.
Press Enter and I will start to guess the number.
My guess is:  500. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : h
My guess is:  250. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : h
My guess is:  125. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : l
My guess is:  187. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : h
My guess is:  156. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : h
My guess is:  140. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : h
My guess is:  132. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : l
My guess is:  136. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : l
My guess is:  138. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : h
My guess is:  137. How did i score? 'l' = too low, 'h' = too high, 'c' = correct : c
So the number is:  137
It was nice to play with you.

[edit] Perl

#!/usr/bin/perl
 
my $min = 1;
my $max = 99;
my $guess = int(rand $max) + $min;
my $tries = 0;
 
print "=>> Think of a number between $min and $max and I'll guess it!\n
Press <ENTER> when are you ready... "
;
 
<STDIN>;
 
{
do {
 
$tries++;
print "\n=>> My guess is: $guess Is your number higher, lower, or equal? (h/l/e)\n> ";
 
my $score = <STDIN>;
 
if ($max <= $min) {
print "\nI give up...\n" and last;
} elsif ($score =~ /^h/i) {
$min = $guess + 1;
} elsif ($score =~ /^l/i) {
$max = $guess;
} elsif ($score =~ /^e/i) {
print "\nI knew it! It took me only $tries tries.\n" and last;
} else {
print "error: invalid score\n";
}
 
$guess = int(($max + $min) / 2);
 
} while(1);
}
=>> Think of a number between 1 and 99 and I'll guess it!

Press <ENTER> when are you ready... 

=>> My guess is: 88. Is your number higher, lower or equal? (h/l/e)
> l

=>> My guess is: 44. Is your number higher, lower or equal? (h/l/e)
> l

=>> My guess is: 22. Is your number higher, lower or equal? (h/l/e)
> h

=>> My guess is: 33. Is your number higher, lower or equal? (h/l/e)
> l

=>> My guess is: 28. Is your number higher, lower or equal? (h/l/e)
> e

I knew it! It took me only 5 tries.

[edit] Perl 6

multi sub MAIN() { MAIN(0, 100) }
multi sub MAIN($min is copy where ($min >= 0), $max is copy where ($max > $min)) {
say "Think of a number between $min and $max and I'll guess it!";
while $min <= $max {
my $guess = (($max + $min)/2).floor;
given lc prompt "My guess is $guess. Is your number higher, lower or equal? " {
when /^e/ { say "I knew it!"; exit }
when /^h/ { $min = $guess + 1 }
when /^l/ { $max = $guess }
default { say "WHAT!?!?!" }
}
}
say "How can your number be both higher and lower than $max?!?!?";
}

You may execute this program with 'perl6 program' or with 'perl6 program min max'. Perl 6 creates a usage for us if we don't give the right parameters. It also parses the parameters for us and provides them via $min and $max. We use multi-subs to provide two MAIN subroutines so the user is able to choose between min and max parameters and no parameters at all, in which case min is set to 0 and max to 100.

[edit] PicoLisp

Translation of: PureBasic
(de guessTheNumber (Min Max)
(prinl "Think of a number between " Min " and " Max ".")
(prinl "On every guess of mine you should state whether my guess was")
(prinl "too high, too low, or equal to your number by typing 'h', 'l', Or '='")
(use Guess
(loop
(NIL (> Max Min)
(prinl "I think somthing is strange here...") )
(prin
"My guess is "
(setq Guess (+ Min (/ (- Max Min) 2)))
",is this correct? " )
(flush)
(NIL
(case (uppc (car (line)))
("H" (setq Max Guess))
("L" (setq Min Guess))
("=" (nil (prinl "I did it!")))
(T (prinl "I do not understand that...")) ) ) ) ) )

Output:

: (guessTheNumber 1 99)
Think of a number between 1 and 99.
On every guess of mine you should state whether my guess was
too high, too low, or equal to your number by typing 'h', 'l', Or '='
My guess is 50,is this correct? h
My guess is 25,is this correct? h
My guess is 13,is this correct? l
My guess is 19,is this correct? l
My guess is 22,is this correct? =
I did it!

[edit] Prolog

min(1). max(10).
 
pick_number(Min, Max) :-
min(Min), max(Max),
format('Pick a number between ~d and ~d, and I will guess it...~nReady? (Enter anything when ready):', [Min, Max]),
read(_).
 
guess_number(Min, Max) :-
Guess is (Min + Max) // 2,
format('I guess ~d...~nAm I correct (c), too low (l), or too high (h)? ', [Guess]),
repeat,
read(Score),
( Score = l -> NewMin is Guess + 1, guess_number(NewMin, Max)
; Score = h -> NewMax is Guess - 1, guess_number(Min, NewMax)
; Score = c -> writeln('I am correct!')
; writeln('Invalid input'),
false
).
 
play :-
pick_number(Min, Max),
guess_number(Min, Max).

Example:

?- play.
Pick a number between 1 and 10, and I will guess it...
Ready? (Enter anything when ready):y.
I guess 5...
Am I correct (c), too low (l), or too high (h)? h.
I guess 2...
Am I correct (c), too low (l), or too high (h)? l.
I guess 3...
Am I correct (c), too low (l), or too high (h)? c.
I'm correct!
true

[edit] PureBasic

min=0
max=100
 
If OpenConsole()
PrintN("Think of a number between "+Str(min)+" and "+Str(max)+".")
PrintN("On every guess of mine you should state whether my guess was")
PrintN("too high, too low, or equal to your number by typing 'h', 'l', Or '='")
Repeat
If max<=min
PrintN("I think somthing is strange here...")
Break
EndIf
Guess=(max-min)/2+min
Print("My guess is "+Str(Guess)+",is this correct? "): Respons.s=UCase(Input())
If Respons="H": max=Guess-1
ElseIf Respons="L": min=Guess+1
ElseIf Respons="="
PrintN("I did it!")
Break
Else
PrintN("I do not understand that...")
EndIf
ForEver
EndIf

[edit] Python

inclusive_range = mn, mx = (1, 10)
 
print('''\
Think of a number between %i and %i and wait for me to guess it.
On every guess of mine you should state whether the guess was
too high, too low, or equal to your number by typing h, l, or =
'''
 % inclusive_range)
 
i = 0
while True:
i += 1
guess = (mn+mx)//2
txt = input("Guess %2i is: %2i. The score for which is (h,l,=): "
 % (i, guess)).strip().lower()[0]
if txt not in 'hl=':
print(" I don't understand your input of '%s' ?" % txt)
continue
if txt == 'h':
mx = guess-1
if txt == 'l':
mn = guess+1
if txt == '=':
print(" Ye-Haw!!")
break
if (mn > mx) or (mn < inclusive_range[0]) or (mx > inclusive_range[1]):
print("Please check your scoring as I cannot find the value")
break
 
print("\nThanks for keeping score.")

Sample Game-play

Think of a number between 1 and 10 and wait for me to guess it.
On every guess of mine you should state whether the guess was
too high, too low, or equal to your number by typing h, l, or =

Guess  1 is:  5. The score for which is (h,l,=): l
Guess  2 is:  8. The score for which is (h,l,=): l
Guess  3 is:  9. The score for which is (h,l,=): l
Guess  4 is: 10. The score for which is (h,l,=): =
  Ye-Haw!!

Thanks for keeping score.

[edit] Obscure solution using bisect module

Hacky solution using a fake list class and the bisect module from the standard library to do the binary search.

Translation of: Go
import bisect
try: input = raw_input
except: pass
 
class GuessNumberFakeList(object):
def __getitem__(self, i):
s = input("Is your number less than or equal to %d?" % i)
return 0 if s.lower().startswith('y') else -1
 
LOWER, UPPER = 0, 100
 
if __name__ == "__main__":
print("""Instructions:
Think of integer number from %d (inclusive) to %d (exclusive) and
I will guess it. After each guess, I will ask you if it is less than
or equal to some number, and you will respond with "yes" or "no".
"""
 % (LOWER, UPPER))
result = bisect.bisect_left(GuessNumberFakeList(), 0, LOWER, UPPER)
print("Your number is %d." % result)
Sample output
Instructions:
Think of integer number from 0 (inclusive) to 100 (exclusive) and
I will guess it. After each guess, I will ask you if it is less than
or equal to some number, and you will respond with "yes" or "no".


Is your number less than or equal to 50?no

Is your number less than or equal to 75?yes

Is your number less than or equal to 63?no

Is your number less than or equal to 69?no

Is your number less than or equal to 72?yes

Is your number less than or equal to 71?no
Your number is 72.

[edit] Racket

#lang racket
 
(define (guess low high)
(define (input-loop available)
(define input (car (string->list (symbol->string (read)))))
(if (member input available)
input
(begin
(printf "Invalid Input\n") (input-loop available))))
 
(define (guess-loop low high)
(define guess (floor (/ (+ low high) 2)))
(printf "My guess is ~a.\n" guess)
(define input (input-loop (list #\c #\l #\h)))
(case input
((#\c) (displayln "I knew it!\n"))
((#\l) (guess-loop low (sub1 guess)))
((#\h) (guess-loop (add1 guess) high))))
 
(printf "Think of a number between ~a and ~a.
Use (h)igh, (l)ow and (c)orrect to guide me.\n" low high)
(guess-loop low high))

Another way with loops and mutation

#lang racket
(define (guess minimum maximum)
(printf "Think of a number from ~a to ~a, use (h)igh, (l)ow and (c)orrect." minimum maximum)
 
(define input "")
 
(do ((guess (round (/ (+ maximum minimum) 2)) (round (/ (+ maximum minimum) 2))))
((string=? input "c"))
(printf "My guess is: ~a\n(h/l/=) > ")
(when (string=? input "h")
(begin (display "OK...")
(set! maximum (sub1 guess))))
(when (string=? input "l")
(begin (display "OK...")
(set! minimum (add1 guess)))))
(displayln "I was RIGHT!"))

[edit] REXX

[edit] with positive integers

This version only handles positive integers.

/*REXX pgm to play guess-the-number (with itself) with positive integers*/
parse arg low high .
if low=='' then low=1
if high=='' then high=1000
?=random(low,high)
say
try="Try to guess my integer (it's between" low 'and' high" inclusive)."
 
do j=1
say try; say
call guesser
select
when guess>? then info=right("It's too high.",40)
when guess<? then info=right("It's too low. ",40)
otherwise leave
end /*select*/
end /*j*/
say
say 'Congratulations! You guessed the secret number in' j "tries."
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────GUESSER subroutine──────────────────*/
guesser: oguess=guess
if pos('high',info)\==0 then high=guess
if pos('low' ,info)\==0 then low =guess
guess=low+(high-low)%2
if guess=oguess then guess=guess+1
say 'My guess is' guess
return

output shown is from playing several games:

Try to guess my number  (it's between 1 and 1000 inclusive).

My guess is 500
                          It's too low.

My guess is 750
                          It's too low.

My guess is 875
                          It's too high.

My guess is 812
                          It's too low.

My guess is 843
                          It's too high.

My guess is 827
                          It's too high.

My guess is 819
                          It's too low.

My guess is 823
                          It's too low.

My guess is 825

Congratulations!  You guessed the secret number in 9 tries.
_________________________________________________________________

Try to guess my number  (it's between 1 and 1000 inclusive).

My guess is 500
                          It's too high.

My guess is 250
                          It's too high.

My guess is 125
                          It's too high.

My guess is 63
                          It's too high.

My guess is 32
                          It's too low.

My guess is 47
                          It's too low.

My guess is 55
                          It's too low.

My guess is 59
                          It's too high.

My guess is 57
                          It's too low.

My guess is 58

Congratulations!  You guessed the secret number in 10 tries.
_________________________________________________________________

Try to guess my number  (it's between 1 and 1000 inclusive).

My guess is 500
                          It's too high.

My guess is 250
                          It's too low.

My guess is 375
                          It's too high.

My guess is 312
                          It's too low.

My guess is 343
                          It's too low.

My guess is 359
                          It's too high.

My guess is 351

Congratulations!  You guessed the secret number in 7 tries.
_________________________________________________________________

Try to guess my number  (it's between 1 and 1000 inclusive).

My guess is 500
                          It's too low.

My guess is 750
                          It's too high.

My guess is 625
                          It's too low.

My guess is 687
                          It's too high.

My guess is 656

Congratulations!  You guessed the secret number in 5 tries.
_________________________________________________________________

Try to guess my number  (it's between 1 and 1000 inclusive).

My guess is 500
                          It's too high.

My guess is 250
                          It's too high.

My guess is 125

Congratulations!  You guessed the secret number in 3 tries.

[edit] with positive numbers

This version handles decimal fractions (method used only generates numbers with a one-digit decimal fraction, but this
REXX program will handle any length of decimal fractions than can be generated with the current numeric digits.

/*REXX pgm to play guess-the-number (with itself) with positive numbers.*/
parse arg low high .
if low=='' then low=1
if high=='' then high=1000
?=random(low*10,high*10)/10 /*make it tough, it may be a fraction.*/
say
try="Try to guess my number (it's between" low 'and' high" inclusive)."
 
do j=1; say try; say
call guesser
select
when guess>? then info=right("It's too high.",40)
when guess<? then info=right("It's too low. ",40)
otherwise leave
end /*select*/
end /*j*/
say
say 'Congratulations! You guessed the secret number in' j "tries."
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────GUESSER subroutine──────────────────*/
guesser: oguess=guess
if pos('high',info)\==0 then high=guess
if pos('low' ,info)\==0 then low =guess
guess=(low+(high-low)/2) / 1
if guess=oguess then guess=guess+1
say 'My guess is' guess
return

output will be about ten times longer (that is, has ten more times the guesses).

[edit] Ruby

Computer plays versus itself

def play(low, high, turns=1)
num = (low + high) / 2
print "guessing #{num}\t"
case is_it?(num)
when 1
puts "too high"
play(low, num - 1, turns + 1)
when -1
puts "too low"
play(num + 1, high, turns + 1)
else
puts "found the number in #{turns} turns."
end
end
 
def is_it?(num)
num <=> $number
end
 
low, high = 1, 100
$number = rand(low .. high)
 
puts "guess a number between #{low} and #{high}"
play(low, high)

Example

guess a number between 1 and 100
guessing 50     too high
guessing 25     too low
guessing 37     too high
guessing 31     too high
guessing 28     too low
guessing 29     too low
guessing 30     found the number in 7 turns.

Since Ruby 2.0 it can be done actually using a binary search (output as above):

r = (1..100)
secret = rand(r)
turns = 0
 
puts "Guess a number between #{r.min} and #{r.max}"
r.bsearch do |guess| # bsearch works on ranges
print "Guessing #{guess} \t"
turns += 1
low_high = secret <=> guess # -1, 0, or 1
puts ["found the number in #{turns} turns", "too low", "too high"][low_high]
low_high
end
 

[edit] Rust

Works with: rustc version 0.11-pre-nightly
use std::io::stdio::stdin;
 
static INITIAL_LOW: int = 1;
static INITIAL_HIGH: int = 100;
 
struct GameState {
low: int,
high: int,
current_guess: int,
number_of_guesses: int,
}
 
impl GameState {
fn new() -> GameState {
return GameState {
low: INITIAL_LOW,
high: INITIAL_HIGH,
current_guess: (INITIAL_LOW + INITIAL_HIGH) / 2,
number_of_guesses: 0
};
}
 
fn guess_higher (&self) -> GameState {
let new_low = self.current_guess;
let new_guess = (self.current_guess + self.high) / 2;
return GameState {
low: new_low,
high: self.high,
current_guess: new_guess,
number_of_guesses: self.number_of_guesses + 1
};
}
 
fn guess_lower(&self) -> GameState {
let new_high = self.current_guess;
let new_guess = (self.current_guess + self.low) / 2;
return GameState {
low: self.low,
high: new_high,
current_guess: new_guess,
number_of_guesses: self.number_of_guesses + 1
};
}
}
 
fn main() {
let mut current_state = GameState::new();
 
let mut stdin = stdin();
 
println!("Hello, please choose a number between {} and {} and remember it.", current_state.high, current_state.low);
println!("Got it? Good. Now I shall guess it using only the power of my mind.\n");
 
loop {
 
println!("My guess is {:d}. Is that too [h]igh, too [l]ow or is it [e]qual to it? ", current_state.current_guess);
println!("(please type h, l or e and then hit enter) (or type q to quit)");
 
let answer_str = match stdin.read_line().ok() {
Some(s) => s.trim().to_owned(),
None => ~""
};
 
match answer_str.as_slice() {
"e" | "E" => {
println!("Woot, I got it in only {} tries!", current_state.number_of_guesses + 1);
break;
}
"l" | "L" => current_state = current_state.guess_higher(),
"h" | "H" => current_state = current_state.guess_lower(),
"q" | "Q" => break,
_ => println!("sorry, I didn't quite get that")
 
}
 
if current_state.low == current_state.high {
println!("Your number must be {}. Or maybe you forgot it? It happens!", current_state.low);
break;
}
if current_state.low > current_state.high {
println!("Uh, I think something went wrong. Entirely my fault, I'm sure!");
break;
}
}
}

[edit] Scheme

Works with: Guile
(define minimum 1)   
(define maximum 100)
 
(display "Enter a number from ")(display minimum)
(display " to ")(display maximum)(display ": ")
(define number (read))
 
(define input "")
 
(do ((guess (round (/ (+ maximum minimum) 2)) (round (/ (+ maximum minimum) 2))))
((string= input "="))
(display "Is it ")(display guess)(display "?\n(h/l/=) > ")
(set! input (symbol->string (read)))
(if (string= input "h") (begin (display "OK...")
(set! maximum (- guess 1))))
(if (string= input "l") (begin (display "OK...")
(set! minimum (+ guess 1)))))
(display "I was RIGHT!\n")

[edit] Seed7

The program reads the possible commands (l, h, c, q) as single keypresses from the KEYBOARD with getc. It is also possible to quit the program with q. The program recognices also a situation when there is only one possible number left and the command is not c.

$ include "seed7_05.s7i";
$ include "keybd.s7i";
 
const proc: main is func
local
var boolean: okay is FALSE;
var boolean: quit is FALSE;
var integer: low is 1;
var integer: high is 1000;
var integer: guess is 0;
var char: command is ' ';
begin
writeln("Choose a number between 1 and 1000.");
write("Press Enter and I will start to guess the number.");
readln;
repeat
guess := low + (high - low) div 2;
write("My guess is: " <& guess);
write(". How did I score (l=too low, h=too high, c=correct, q=quit)? ");
flush(OUT);
repeat
command := lower(getc(KEYBOARD));
until command in {'l', 'h', 'c', 'q'};
writeln(command);
case command of
when {'l'}: low := succ(guess);
when {'h'}: high := pred(guess);
when {'c'}: okay := TRUE;
when {'q'}: quit := TRUE;
end case;
until quit or okay or low > high;
if not quit then
writeln("So the number is: " <& guess);
if low > high then
writeln("Why did you cheat?");
end if;
end if;
writeln("It was nice to play with you.");
end func;

Example

Choose a number between 1 and 1000.
Press Enter and I will start to guess the number.
My guess is: 500. How did I score (l=too low, h=too high, c=correct, q=quit)? h
My guess is: 250. How did I score (l=too low, h=too high, c=correct, q=quit)? l
My guess is: 375. How did I score (l=too low, h=too high, c=correct, q=quit)? h
My guess is: 312. How did I score (l=too low, h=too high, c=correct, q=quit)? l
My guess is: 343. How did I score (l=too low, h=too high, c=correct, q=quit)? l
My guess is: 359. How did I score (l=too low, h=too high, c=correct, q=quit)? l
My guess is: 367. How did I score (l=too low, h=too high, c=correct, q=quit)? h
My guess is: 363. How did I score (l=too low, h=too high, c=correct, q=quit)? l
My guess is: 365. How did I score (l=too low, h=too high, c=correct, q=quit)? c
So the number is: 365
It was nice to play with you.

[edit] Smalltalk

Works with: Pharo version 1.4

Create a class like this:

Object subclass: #NumberGuesser
instanceVariableNames: ''
classVariableNames: ''
poolDictionaries: ''
category: 'Rosettacode'
 

Enter these methods into it:

playBetween: low and: high
Transcript clear.
number := (low to: high) atRandom.
self playBetween: low and: high atTurn: 1.
 
playBetween: low and: high atTurn: turn
| guess |
guess := (low + ((high - low) / 2)) asInteger.
self showGuessing: guess atTurn: turn.
true caseOf: {
[number > guess] ->
[self showNumberBeing: #low. self playBetween: guess and: high atTurn: turn+1 ].
[number < guess] ->
[self showNumberBeing: #high. self playBetween: low and: guess atTurn: turn+1 ].
[true] ->
[self showNumberFoundAtTurnNr: turn ] }.
 
showGuessing: guess atTurn: turn
Transcript show: ('{1}. guessing: {2}' format: {turn asString. guess asString}).
 
showNumberBeing: comparisonToken
Transcript show: ' ==> too ', (comparisonToken asString); cr.
 
showNumberFoundAtTurnNr: turn
Transcript show: (' ==> found the number in {1} turn(s).' format: {turn asString}); cr.
 

If you'd rather not use caseOf: you can write playBetween:and:atTurn: like this:

 
playBetween: low and: high atTurn: turn
| guess |
guess := (low + ((high - low) / 2)) asInteger.
self showGuessing: guess atTurn: turn.
(guess = number)
ifTrue: [self showNumberFoundAtTurnNr: turn ]
ifFalse: [
(number > guess)
ifTrue: [self showNumberBeing: #low. self playBetween: guess and: high atTurn: turn+1 ]
ifFalse: [self showNumberBeing: #high. self playBetween: low and: guess atTurn: turn+1]].
 

And evaluate this in a Workspace:

g := NumberGuesser new.
g playBetween: 1 and: 100.
 

Sample output:

1. guessing: 50 ==> too low
2. guessing: 75 ==> too low
3. guessing: 87 ==> too high
4. guessing: 81 ==> too low
5. guessing: 84 ==> too low
6. guessing: 85 ==> found the number in 6 turn(s).

[edit] Standard ML

A clever solution that uses the built-in binary search functions with a virtual list.

Works with: SML/NJ
Translation of: Go
structure GuessNumberHelper : MONO_ARRAY = struct
type elem = order
type array = int * int
fun length (lo, hi) = hi - lo
fun sub ((lo, hi), i) =
let
val n = lo + i
in
print ("My guess is: " ^ Int.toString (lo+i) ^ ". Is it too high, too low, or correct? (H/L/C) ");
let
val str = valOf (TextIO.inputLine TextIO.stdIn)
in
case Char.toLower (String.sub (str, 0)) of
#"l" => GREATER
| #"h" => LESS
| #"c" => EQUAL
end
end
 
(* dummy implementations for not-needed functions *)
type vector = unit
val maxLen = Array.maxLen
fun update _ = raise Domain
fun array _ = raise Domain
fun fromList _ = raise Domain
fun tabulate _ = raise Domain
fun vector _ = raise Domain
fun copy _ = raise Domain
fun copyVec _ = raise Domain
fun appi _ = raise Domain
fun app _ = raise Domain
fun modifyi _ = raise Domain
fun modify _ = raise Domain
fun foldli _ = raise Domain
fun foldl _ = raise Domain
fun foldri _ = raise Domain
fun foldr _ = raise Domain
fun findi _ = raise Domain
fun find _ = raise Domain
fun exists _ = raise Domain
fun all _ = raise Domain
fun collate _ = raise Domain
end
 
structure GuessNumberBSearch = BSearchFn (GuessNumberHelper)
 
val lower = 0
val upper = 100;
 
print ("Instructions:\n" ^
"Think of integer number from " ^ Int.toString lower ^
" (inclusive) to " ^ Int.toString upper ^ " (exclusive) and\n" ^
"I will guess it. After each guess, you respond with L, H, or C depending\n" ^
"on if my guess was too low, too high, or correct.\n");
 
case GuessNumberBSearch.bsearch (fn (_, x) => x) ((), (lower, upper)) of
NONE => print "That is impossible.\n"
| SOME (result, _) => print ("Your number is " ^ Int.toString result ^ ".\n")

[edit] Tcl

set from 1
set to 10
fconfigure stdout -buffering none
while 1 {
set guess [expr {($from+$to) / 2}]
puts -nonewline "Guess: $guess\tWas it lower (<) equal (=) or higher (>)? "
switch -- [gets stdin] {
< { set from [expr {$guess + 1}] }
> { set to [expr {$guess - 1}] }
= {
puts "Found it: $guess"
break
}
default {
puts "What sort of a response was that?!"
}
}
if {$to < $from} {
puts "No answer possible?!"
break
}
}

Sample run:

Guess: 5	Was it lower (<) equal (=) or higher (>)? <
Guess: 8	Was it lower (<) equal (=) or higher (>)? >
Guess: 6	Was it lower (<) equal (=) or higher (>)? =
Found it: 6


[edit] VBA

 
Sub GuessNumberPlayer()
Dim iGuess As Integer, iLow As Integer, iHigh As Integer, iCount As Integer
Dim vSolved As Variant
On Error GoTo ErrHandler
MsgBox "Pick a number between 1 and 100. I will guess it!", vbInformation + vbOKOnly, "Rosetta Code | Guess the Number Player"
iCount = 0
iLow = 1
iHigh = 100
Do While Not vSolved = "Y"
iGuess = Application.WorksheetFunction.RandBetween(iLow, iHigh)
iCount = iCount + 1
CheckGuess:
vSolved = InputBox("My guess: " & iGuess & vbCr & vbCr & "Y = Yes, correct guess" & vbCr & _
"H = your number is higher" & vbCr & "L = your number is lower" & vbCr & "X = exit game", "Rosetta Code | Guess the Number Player | Guess " & iCount)
Select Case vSolved
Case "Y", "y": GoTo CorrectGuess
Case "X", "x": Exit Sub
Case "H", "h": iLow = iGuess + 1
Case "L", "l": iHigh = iGuess - 1
Case Else: GoTo CheckGuess
End Select
Loop
CorrectGuess:
MsgBox "I guessed number " & iGuess & " in just " & iCount & " attempts!", vbExclamation + vbOKOnly, "Rosetta Code | Guess the Number Player"
Exit Sub
ErrHandler:
MsgBox "Not possible. Were you cheating?!", vbCritical + vbOKOnly, "Rosetta Code | Guess the Number Player | ERROR!"
End Sub
 

[edit] XPL0

include c:\cxpl\codes;  \intrinsic 'code' declarations
int Hi, Lo, Guess;
[Text(0, "Think of a number between 1 and 100 then press a key.");
if ChIn(1) then [];
Lo:= 1; Hi:= 101;
loop [Guess:= (Lo+Hi)/2;
Text(0, "^M^JIs it "); IntOut(0, Guess);
Text(0, " (Y = yes, H = too high, L = too low)? ");
case ChIn(1) of
^L,^l: Lo:= Guess;
^H,^h: Hi:= Guess;
^Y,^y: quit
other ChOut(0, 7\bel\);
];
Text(0, "^M^JYippee!");
]

Example output:

Think of a number between 1 and 100 then press a key.
Is it 51 (Y = yes, H = too high, L = too low)? H
Is it 26 (Y = yes, H = too high, L = too low)? H
Is it 13 (Y = yes, H = too high, L = too low)? L
Is it 19 (Y = yes, H = too high, L = too low)? H
Is it 16 (Y = yes, H = too high, L = too low)? L
Is it 17 (Y = yes, H = too high, L = too low)? Y
Yippee!
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