Evaluate binomial coefficients: Difference between revisions
→Functional: Removed obfuscated Python solution. |
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return int( reduce( mul, range((n-r+1), n+1), 1) / |
return int( reduce( mul, range((n-r+1), n+1), 1) / |
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reduce( mul, range(1,r+1), 1) )</lang> |
reduce( mul, range(1,r+1), 1) )</lang> |
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Or, updating for Python 3, and abstracting a little more for legibility and ease of reuse, while currying for ease of mapping and general composition: |
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<lang python>from functools import reduce |
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# binomialCoefficient :: Int -> Int -> Int |
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def binomialCoefficient(n): |
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return lambda k: product( |
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enumFromTo(1 + k)(n) |
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) // factorial(n - k) |
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# GENERIC ------------------------------------------------- |
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# enumFromTo :: Int -> Int -> [Int] |
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def enumFromTo(m): |
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return lambda n: range(m, 1 + n) |
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# factorial :: Int -> Int |
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def factorial(x): |
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return product(enumFromTo(1)(x)) |
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# product :: [Num] -> Num |
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def product(xs): |
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return reduce(lambda a, b: a * b, xs, 1) |
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# TESTS --------------------------------------------------- |
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print( |
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binomialCoefficient(5)(3) |
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) |
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# k=0 to k=5, where n=5 |
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print( |
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list(map( |
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binomialCoefficient(5), |
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enumFromTo(0)(5) |
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)) |
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)</lang> |
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{{Out}} |
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<pre>10 |
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[1, 5, 10, 10, 5, 1]</pre> |
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=={{header|R}}== |
=={{header|R}}== |
Revision as of 10:15, 21 February 2019
![Task](http://static.miraheze.org/rosettacodewiki/thumb/b/ba/Rcode-button-task-crushed.png/64px-Rcode-button-task-crushed.png)
You are encouraged to solve this task according to the task description, using any language you may know.
This programming task, is to calculate ANY binomial coefficient.
However, it has to be able to output , which is 10.
This formula is recommended:
See Also:
The number of samples of size k from n objects.
With combinations and permutations generation tasks.
Order Unimportant Order Important Without replacement Task: Combinations Task: Permutations With replacement Task: Combinations with repetitions Task: Permutations with repetitions
360 Assembly
Very compact version. <lang 360asm>* Evaluate binomial coefficients - 29/09/2015 BINOMIAL CSECT
USING BINOMIAL,R15 set base register SR R4,R4 clear for mult and div LA R5,1 r=1 LA R7,1 i=1 L R8,N m=n
LOOP LR R4,R7 do while i<=k
C R4,K i<=k BH LOOPEND if not then exit while MR R4,R8 r*m DR R4,R7 r=r*m/i LA R7,1(R7) i=i+1 BCTR R8,0 m=m-1 B LOOP loop while
LOOPEND XDECO R5,PG edit r
XPRNT PG,12 print r XR R15,R15 set return code BR R14 return to caller
N DC F'10' <== input value K DC F'4' <== input value PG DS CL12 buffer
YREGS END BINOMIAL</lang>
- Output:
210
ABAP
<lang ABAP>CLASS lcl_binom DEFINITION CREATE PUBLIC.
PUBLIC SECTION. CLASS-METHODS: calc IMPORTING n TYPE i k TYPE i RETURNING VALUE(r_result) TYPE f.
ENDCLASS.
CLASS lcl_binom IMPLEMENTATION.
METHOD calc.
r_result = 1. DATA(i) = 1. DATA(m) = n.
WHILE i <= k. r_result = r_result * m / i. i = i + 1. m = m - 1. ENDWHILE.
ENDMETHOD.
ENDCLASS.</lang>
- Output:
lcl_binom=>calc( n = 5 k = 3 ) 1,0000000000000000E+01 lcl_binom=>calc( n = 60 k = 30 ) 1,1826458156486142E+17
ACL2
<lang Lisp>(defun fac (n)
(if (zp n) 1 (* n (fac (1- n)))))
(defun binom (n k)
(/ (fac n) (* (fac (- n k)) (fac k)))</lang>
Ada
<lang Ada> with Ada.Text_IO; use Ada.Text_IO; procedure Test_Binomial is
function Binomial (N, K : Natural) return Natural is Result : Natural := 1; M : Natural; begin if N < K then raise Constraint_Error; end if; if K > N/2 then -- Use symmetry M := N - K; else M := K; end if; for I in 1..M loop Result := Result * (N - M + I) / I; end loop; return Result; end Binomial;
begin
for N in 0..17 loop for K in 0..N loop Put (Integer'Image (Binomial (N, K))); end loop; New_Line; end loop;
end Test_Binomial; </lang>
- Output:
1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1 1 9 36 84 126 126 84 36 9 1 1 10 45 120 210 252 210 120 45 10 1 1 11 55 165 330 462 462 330 165 55 11 1 1 12 66 220 495 792 924 792 495 220 66 12 1 1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1 1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1 1 15 105 455 1365 3003 5005 6435 6435 5005 3003 1365 455 105 15 1 1 16 120 560 1820 4368 8008 11440 12870 11440 8008 4368 1820 560 120 16 1 1 17 136 680 2380 6188 12376 19448 24310 24310 19448 12376 6188 2380 680 136 17 1
ALGOL 68
Iterative - unoptimised
- note: This specimen retains the original C coding style.
<lang algol68>PROC factorial = (INT n)INT: (
INT result; result := 1; FOR i TO n DO result *:= i OD; result
);
PROC choose = (INT n, INT k)INT: (
INT result;
- Note: code can be optimised here as k < n #
result := factorial(n) OVER (factorial(k) * factorial(n - k)); result
);
test:(
print((choose(5, 3), new line))
)</lang>
- Output:
+10
ALGOL W
<lang algolw>begin
% calculates n!/k! % integer procedure factorialOverFactorial( integer value n, k ) ; if k > n then 0 else if k = n then 1 else % k < n % begin integer f; f := 1; for i := k + 1 until n do f := f * i; f end factorialOverFactorial ;
% calculates n! % integer procedure factorial( integer value n ) ; begin integer f; f := 1; for i := 2 until n do f := f * i; f end factorial ;
% calculates the binomial coefficient of (n k) % % uses the factorialOverFactorial procedure for a slight optimisation % integer procedure binomialCoefficient( integer value n, k ) ; if ( n - k ) > k then factorialOverFactorial( n, n - k ) div factorial( k ) else factorialOverFactorial( n, k ) div factorial( n - k );
% display the binomial coefficient of (5 3) % write( binomialCoefficient( 5, 3 ) )
end.</lang>
AppleScript
Imperative
<lang AppleScript>set n to 5 set k to 3
on calculateFactorial(val) set partial_factorial to 1 as integer repeat with i from 1 to val set factorial to i * partial_factorial set partial_factorial to factorial end repeat return factorial end calculateFactorial
set n_factorial to calculateFactorial(n) set k_factorial to calculateFactorial(k) set n_minus_k_factorial to calculateFactorial(n - k)
return n_factorial / (n_minus_k_factorial) * 1 / (k_factorial) as integer </lang>
Functional
Using a little more abstraction, for readability and for ease of both re-use and refactoring:
<lang applescript>-- factorial :: Int -> Int on factorial(n)
product(enumFromTo(1, n))
end factorial
-- binomialCoefficient :: Int -> Int -> Int
on binomialCoefficient(n, k)
factorial(n) div (factorial(n - k) * (factorial(k)))
end binomialCoefficient
-- Or, by reduction:
-- binomialCoefficient2 :: Int -> Int -> Int on binomialCoefficient2(n, k)
product(enumFromTo(1 + k, n)) div (factorial(n - k))
end binomialCoefficient2
-- TEST -----------------------------------------------------
on run
{binomialCoefficient(5, 3), binomialCoefficient2(5, 3)} --> {10, 10}
end run
-- GENERAL -------------------------------------------------
-- enumFromTo :: Int -> Int -> [Int] on enumFromTo(m, n)
if m ≤ n then set lst to {} repeat with i from m to n set end of lst to i end repeat return lst else return {} end if
end enumFromTo
-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
tell mReturn(f) set v to startValue set lng to length of xs repeat with i from 1 to lng set v to |λ|(v, item i of xs, i, xs) end repeat return v end tell
end foldl
-- Lift 2nd class handler function into 1st class script wrapper -- mReturn :: First-class m => (a -> b) -> m (a -> b) on mReturn(f)
if script is class of f then f else script property |λ| : f end script end if
end mReturn
-- product :: [Num] -> Num on product(xs)
script multiply on |λ|(a, b) a * b end |λ| end script foldl(multiply, 1, xs)
end product</lang>
- Output:
{10, 10}
AutoHotkey
<lang autohotkey>MsgBox, % Round(BinomialCoefficient(5, 3))
- ---------------------------------------------------------------------------
BinomialCoefficient(n, k) {
- ---------------------------------------------------------------------------
r := 1 Loop, % k < n - k ? k : n - k { r *= n - A_Index + 1 r /= A_Index } Return, r
}</lang> Message box shows:
10
AWK
<lang AWK>
- syntax: GAWK -f EVALUATE_BINOMIAL_COEFFICIENTS.AWK
BEGIN {
main(5,3) main(100,2) main(33,17) exit(0)
} function main(n,k, i,r) {
r = 1 for (i=1; i<k+1; i++) { r *= (n - i + 1) / i } printf("%d %d = %d\n",n,k,r)
} </lang>
- Output:
5 3 = 10 100 2 = 4950 33 17 = 1166803110
Batch File
<lang dos>@echo off & setlocal
if "%~2"=="" ( echo Usage: %~nx0 n k && goto :EOF )
call :binom binom %~1 %~2 1>&2 set /P "=%~1 choose %~2 = "<NUL echo %binom%
goto :EOF
- binom <var_to_set> <N> <K>
setlocal set /a coeff=1, nk=%~2 - %~3 + 1 for /L %%I in (%nk%, 1, %~2) do set /a coeff *= %%I for /L %%I in (1, 1, %~3) do set /a coeff /= %%I endlocal && set "%~1=%coeff%" goto :EOF</lang>
- Output:
> binom.bat 5 3 5 choose 3 = 10 > binom.bat 100 2 100 choose 2 = 4950
The string n choose k =
is output to stderr, while the result is echoed to stdout. This should allow capturing the result with a for /f
loop without needing to define tokens or delims.
But...
> binom.bat 33 17 33 choose 17 = 0 > binom.bat 15 10 15 choose 10 = -547
The Windows cmd console only handles 32-bit integers. If a factoral exceeds 2147483647 at any point, set /a
will choke and roll over to a negative value, giving unexpected results. Unfortunately, this is as good as it gets for pure batch.
BBC BASIC
<lang bbcbasic> @%=&1010
PRINT "Binomial (5,3) = "; FNbinomial(5, 3) PRINT "Binomial (100,2) = "; FNbinomial(100, 2) PRINT "Binomial (33,17) = "; FNbinomial(33, 17) END DEF FNbinomial(N%, K%) LOCAL R%, D% R% = 1 : D% = N% - K% IF D% > K% THEN K% = D% : D% = N% - K% WHILE N% > K% R% *= N% N% -= 1 WHILE D% > 1 AND (R% MOD D%) = 0 R% /= D% D% -= 1 ENDWHILE ENDWHILE = R%
</lang>
- Output:
Binomial (5,3) = 10 Binomial (100,2) = 4950 Binomial (33,17) = 1166803110
Bracmat
<lang bracmat>(binomial=
n k coef
. !arg:(?n,?k)
& (!n+-1*!k:<!k:?k|) & 1:?coef & whl ' ( !k:>0 & !coef*!n*!k^-1:?coef & !k+-1:?k & !n+-1:?n ) & !coef
);
binomial$(5,3) 10 </lang>
Burlesque
<lang burlesque> blsq ) 5 3nr 10 </lang>
C
<lang C>#include <stdio.h>
- include <limits.h>
/* We go to some effort to handle overflow situations */
static unsigned long gcd_ui(unsigned long x, unsigned long y) {
unsigned long t; if (y < x) { t = x; x = y; y = t; } while (y > 0) { t = y; y = x % y; x = t; /* y1 <- x0 % y0 ; x1 <- y0 */ } return x;
}
unsigned long binomial(unsigned long n, unsigned long k) {
unsigned long d, g, r = 1; if (k == 0) return 1; if (k == 1) return n; if (k >= n) return (k == n); if (k > n/2) k = n-k; for (d = 1; d <= k; d++) { if (r >= ULONG_MAX/n) { /* Possible overflow */ unsigned long nr, dr; /* reduced numerator / denominator */ g = gcd_ui(n, d); nr = n/g; dr = d/g; g = gcd_ui(r, dr); r = r/g; dr = dr/g; if (r >= ULONG_MAX/nr) return 0; /* Unavoidable overflow */ r *= nr; r /= dr; n--; } else { r *= n--; r /= d; } } return r;
}
int main() {
printf("%lu\n", binomial(5, 3)); printf("%lu\n", binomial(40, 19)); printf("%lu\n", binomial(67, 31)); return 0;
}</lang>
- Output:
10 131282408400 11923179284862717872
C++
<lang cpp>double Factorial(double nValue)
{ double result = nValue; double result_next; double pc = nValue; do { result_next = result*(pc-1); result = result_next; pc--; }while(pc>2); nValue = result; return nValue; }
double binomialCoefficient(double n, double k)
{ if (abs(n - k) < 1e-7 || k < 1e-7) return 1.0; if( abs(k-1.0) < 1e-7 || abs(k - (n-1)) < 1e-7)return n; return Factorial(n) /(Factorial(k)*Factorial((n - k))); }
</lang>
Implementation: <lang cpp>int main() {
cout<<"The Binomial Coefficient of 5, and 3, is equal to: "<< binomialCoefficient(5,3); cin.get();
}</lang>
- Output:
The Binomial Coefficient of 5, and 3, is equal to: 10
C#
<lang csharp>using System;
namespace BinomialCoefficients {
class Program { static void Main(string[] args) { ulong n = 1000000, k = 3; ulong result = biCoefficient(n, k); Console.WriteLine("The Binomial Coefficient of {0}, and {1}, is equal to: {2}", n, k, result); Console.ReadLine(); }
static int fact(int n) { if (n == 0) return 1; else return n * fact(n - 1); }
static ulong biCoefficient(ulong n, ulong k) { if (k > n - k) { k = n - k; }
ulong c = 1; for (uint i = 0; i < k; i++) { c = c * (n - i); c = c / (i + 1); } return c; } }
}</lang>
Clojure
<lang clojure>(defn binomial-coefficient [n k]
(let [rprod (fn [a b] (reduce * (range a (inc b))))] (/ (rprod (- n k -1) n) (rprod 1 k))))</lang>
CoffeeScript
<lang coffeescript> binomial_coefficient = (n, k) ->
result = 1 for i in [0...k] result *= (n - i) / (i + 1) result
n = 5 for k in [0..n]
console.log "binomial_coefficient(#{n}, #{k}) = #{binomial_coefficient(n,k)}"
</lang>
- Output:
> coffee binomial.coffee binomial_coefficient(5, 0) = 1 binomial_coefficient(5, 1) = 5 binomial_coefficient(5, 2) = 10 binomial_coefficient(5, 3) = 10 binomial_coefficient(5, 4) = 5 binomial_coefficient(5, 5) = 1
Common Lisp
<lang lisp> (defun choose (n k)
(labels ((prod-enum (s e)
(do ((i s (1+ i)) (r 1 (* i r))) ((> i e) r))) (fact (n) (prod-enum 1 n)))
(/ (prod-enum (- (1+ n) k) n) (fact k))))
</lang>
D
<lang d>T binomial(T)(in T n, T k) pure nothrow {
if (k > (n / 2)) k = n - k; T bc = 1; foreach (T i; T(2) .. k + 1) bc = (bc * (n - k + i)) / i; return bc;
}
void main() {
import std.stdio, std.bigint;
foreach (const d; [[5, 3], [100, 2], [100, 98]]) writefln("(%3d %3d) = %s", d[0], d[1], binomial(d[0], d[1])); writeln("(100 50) = ", binomial(100.BigInt, 50.BigInt));
}</lang>
- Output:
( 5 3) = 2 (100 2) = 50 (100 98) = 50 (100 50) = 1976664223067613962806675336
The above wouldn't work for me (100C50 correctly gives 100891344545564193334812497256). This next one is a translation of C#: <lang d>T BinomialCoeff(T)(in T n, in T k) {
T nn = n, kk = k, c = cast(T)1;
if (kk > nn - kk) kk = nn - kk;
for (T i = cast(T)0; i < kk; i++) { c = c * (nn - i); c = c / (i + cast(T)1); }
return c;
}
void main() {
import std.stdio, std.bigint;
BinomialCoeff(10UL, 3UL).writeln; BinomialCoeff(100.BigInt, 50.BigInt).writeln;
}</lang>
- Output:
120 100891344545564193334812497256
dc
<lang dc>[sx1q]sz[d0=zd1-lfx*]sf[skdlfxrlk-lfxlklfx*/]sb</lang>
Demonstration:
<lang dc>5 3lbxp</lang> 10
Annotated version:
<lang dc>[ macro z: factorial base case when n is (z)ero ]sx [sx [ x is our dump register; get rid of extraneous copy of n we no longer need]sx
1 [ return value is 1 ]sx q] [ abort processing of calling macro ]sx
sz
[ macro f: factorial ]sx [
d [ duplicate the input (n) ]sx 0 =z [ if n is zero, call z, which stops here and returns 1 ]sx d [ otherwise, duplicate n again ]sx 1 - [ subtract 1 ]sx lfx [ take the factorial ]sx * [ we have (n-1)!; multiply it by the copy of n to get n! ]sx
] sf
[ macro b(n,k): binomial function (n choose k).
straightforward RPN version of formula.]sx [ sk [ remember k. stack: n ]sx d [ duplicate: n n ]sx lfx [ call factorial: n n! ]sx r [ swap: n! n ]sx lk [ load k: n! n k ]sx - [ subtract: n! n-k ]sx lfx [ call factorial: n! (n-k)! ]sx lk [ load k: n! (n-k)! k ]sx lfx [ call factorial; n! (n-k)! k! ]sx * [ multiply: n! (n-k)!k! ]sx / [ divide: n!/(n-k)!k! ]sx
] sb
5 3 lb x p [print(5 choose 3)]sx</lang>
Delphi
<lang Delphi>program Binomial;
{$APPTYPE CONSOLE}
function BinomialCoff(N, K: Cardinal): Cardinal; var
L: Cardinal;
begin
if N < K then Result:= 0 // Error else begin if K > N - K then K:= N - K; // Optimization Result:= 1; L:= 0; while L < K do begin Result:= Result * (N - L); Inc(L); Result:= Result div L; end; end;
end;
begin
Writeln('C(5,3) is ', BinomialCoff(5, 3)); ReadLn;
end.</lang>
Elixir
<lang elixir>defmodule RC do
def choose(n,k) when is_integer(n) and is_integer(k) and n>=0 and k>=0 and n>=k do if k==0, do: 1, else: choose(n,k,1,1) end def choose(n,k,k,acc), do: div(acc * (n-k+1), k) def choose(n,k,i,acc), do: choose(n, k, i+1, div(acc * (n-i+1), i))
end
IO.inspect RC.choose(5,3) IO.inspect RC.choose(60,30)</lang>
- Output:
10 118264581564861424
Erlang
<lang erlang> choose(N, 0) -> 1; choose(N, K) when is_integer(N), is_integer(K), (N >= 0), (K >= 0), (N >= K) ->
choose(N, K, 1, 1).
choose(N, K, K, Acc) ->
(Acc * (N-K+1)) div K;
choose(N, K, I, Acc) ->
choose(N, K, I+1, (Acc * (N-I+1)) div I).
</lang>
ERRE
<lang>PROGRAM BINOMIAL
!$DOUBLE
PROCEDURE BINOMIAL(N,K->BIN)
LOCAL R,D R=1 D=N-K IF D>K THEN K=D D=N-K END IF WHILE N>K DO R*=N N-=1 WHILE D>1 AND (R-D*INT(R/D))=0 DO R/=D D-=1 END WHILE END WHILE BIN=R
END PROCEDURE
BEGIN
BINOMIAL(5,3->BIN) PRINT("Binomial (5,3) = ";BIN) BINOMIAL(100,2->BIN) PRINT("Binomial (100,2) = ";BIN) BINOMIAL(33,17->BIN) PRINT("Binomial (33,17) = ";BIN)
END PROGRAM </lang>
- Output:
Binomial (5,3) = 10 Binomial (100,2) = 4950 Binomial (33,17) = 1166803110
Factor
<lang factor>
- fact ( n -- n-factorial )
dup 0 = [ drop 1 ] [ dup 1 - fact * ] if ;
- choose ( n k -- n-choose-k )
2dup - [ fact ] tri@ * / ;
! outputs 10 5 3 choose .
! alternative using folds USE: math.ranges
! (product [n..k+1] / product [n-k..1])
- choose-fold ( n k -- n-choose-k )
2dup 1 + [a,b] product -rot - 1 [a,b] product / ;
</lang>
F#
<lang fsharp> let choose n k = List.fold (fun s i -> s * (n-i+1)/i ) 1 [1..k] </lang>
Forth
<lang forth>: choose ( n k -- nCk ) 1 swap 0 ?do over i - i 1+ */ loop nip ;
5 3 choose . \ 10
33 17 choose . \ 1166803110</lang>
Fortran
<lang fortran>program test_choose
implicit none
write (*, '(i0)') choose (5, 3)
contains
function factorial (n) result (res)
implicit none integer, intent (in) :: n integer :: res integer :: i
res = product ((/(i, i = 1, n)/))
end function factorial
function choose (n, k) result (res)
implicit none integer, intent (in) :: n integer, intent (in) :: k integer :: res
res = factorial (n) / (factorial (k) * factorial (n - k))
end function choose
end program test_choose</lang>
- Output:
10
FreeBASIC
<lang freebasic>' FB 1.05.0 Win64
Function factorial(n As Integer) As Integer
If n < 1 Then Return 1 Dim product As Integer = 1 For i As Integer = 2 To n product *= i Next Return Product
End Function
Function binomial(n As Integer, k As Integer) As Integer
If n < 0 OrElse k < 0 OrElse n <= k Then Return 1 Dim product As Integer = 1 For i As Integer = n - k + 1 To n Product *= i Next Return product \ factorial(k)
End Function
For n As Integer = 0 To 14
For k As Integer = 0 To n Print Using "####"; binomial(n, k); Print" "; Next k Print
Next n
Print Print "Press any key to quit" Sleep</lang>
- Output:
1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1 1 9 36 84 126 126 84 36 9 1 1 10 45 120 210 252 210 120 45 10 1 1 11 55 165 330 462 462 330 165 55 11 1 1 12 66 220 495 792 924 792 495 220 66 12 1 1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1 1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1
Frink
Frink has a built-in efficient function to find binomial coefficients. It produces arbitrarily-large integers. <lang frink> println[binomial[5,3]] </lang>
FunL
FunL has pre-defined function choose
in module integers
, which is defined as:
<lang funl>def
choose( n, k ) | k < 0 or k > n = 0 choose( n, 0 ) = 1 choose( n, n ) = 1 choose( n, k ) = product( [(n - i)/(i + 1) | i <- 0:min( k, n - k )] )
println( choose(5, 3) ) println( choose(60, 30) )</lang>
- Output:
10 118264581564861424
Here it is defined using the recommended formula for this task. <lang funl>import integers.factorial
def
binomial( n, k ) | k < 0 or k > n = 0 binomial( n, k ) = factorial( n )/factorial( n - k )/factorial( k )</lang>
GAP
<lang gap># Built-in Binomial(5, 3);
- 10</lang>
Go
<lang go>package main import "fmt" import "math/big"
func main() {
fmt.Println(new(big.Int).Binomial(5, 3)) fmt.Println(new(big.Int).Binomial(60, 30))
}</lang>
- Output:
10 118264581564861424
Golfscript
Actually evaluating n!/(k! (n-k)!): <lang golfscript>;5 3 # Set up demo input {),(;{*}*}:f; # Define a factorial function .f@.f@/\@-f/</lang> But Golfscript is meant for golfing, and it's shorter to calculate :
<lang golfscript>;5 3 # Set up demo input 1\,@{1$-@\*\)/}+/</lang>
Groovy
Solution: <lang groovy>def factorial = { x ->
assert x > -1 x == 0 ? 1 : (1..x).inject(1G) { BigInteger product, BigInteger factor -> product *= factor }
}
def combinations = { n, k ->
assert k >= 0 assert n >= k factorial(n).intdiv(factorial(k)*factorial(n-k))
}</lang>
Test: <lang groovy>assert combinations(20, 0) == combinations(20, 20) assert combinations(20, 10) == (combinations(19, 9) + combinations(19, 10)) assert combinations(5, 3) == 10 println combinations(5, 3)</lang>
- Output:
10
Haskell
The only trick here is realizing that everything's going to divide nicely, so we can use div instead of (/).
<lang haskell> choose :: (Integral a) => a -> a -> a choose n k = product [k+1..n] `div` product [1..n-k] </lang>
<lang haskell>> 5 `choose` 3 10</lang>
Or, generate the binomial coefficients iteratively to avoid computing with big numbers:
<lang haskell> choose :: (Integral a) => a -> a -> a choose n k = foldl (\z i -> (z * (n-i+1)) `div` i) 1 [1..k] </lang>
Or using "caching":
<lang haskell>coeffs = iterate next [1]
where next ns = zipWith (+) (0:ns) $ ns ++ [0]
main = print $ coeffs !! 5 !! 3</lang>
HicEst
<lang HicEst>WRITE(Messagebox) BinomCoeff( 5, 3) ! displays 10
FUNCTION factorial( n )
factorial = 1 DO i = 1, n factorial = factorial * i ENDDO
END
FUNCTION BinomCoeff( n, k )
BinomCoeff = factorial(n)/factorial(n-k)/factorial(k)
END</lang>
Icon and Unicon
<lang Icon>link math, factors
procedure main() write("choose(5,3)=",binocoef(5,3)) end</lang>
- Output:
choose(5,3)=10
math provides binocoef and factors provides factorial.
<lang Icon>procedure binocoef(n, k) #: binomial coefficient
k := integer(k) | fail n := integer(n) | fail
if (k = 0) | (n = k) then return 1
if 0 <= k <= n then return factorial(n) / (factorial(k) * factorial(n - k)) else fail
end
procedure factorial(n) #: return n! (n factorial)
local i
n := integer(n) | runerr(101, n)
if n < 0 then fail
i := 1
every i *:= 1 to n
return i
end</lang>
IS-BASIC
<lang IS-BASIC>100 PROGRAM "Binomial.bas" 110 PRINT "Binomial (5,3) =";BINOMIAL(5,3) 120 DEF BINOMIAL(N,K) 130 LET R=1:LET D=N-K 140 IF D>K THEN LET K=D:LET D=N-K 150 DO WHILE N>K 160 LET R=R*N:LET N=N-1 170 DO WHILE D>1 AND MOD(R,D)=0 180 LET R=R/D:LET D=D-1 190 LOOP 200 LOOP 210 LET BINOMIAL=R 220 END DEF</lang>
J
Solution:
The dyadic form of the primitive !
([Out of]) evaluates binomial coefficients directly.
Example usage: <lang j> 3 ! 5 10</lang>
Java
<lang java>public class Binomial {
private static long binomial(int n, int k) { if (k>n-k) k=n-k; long b=1; for (int i=1, m=n; i<=k; i++, m--) b=b*m/i; return b; }
public static void main(String[] args) { System.out.println(binomial(5, 3)); }
}</lang>
- Output:
10
<lang java>public class Binom {
public static double binomCoeff(double n, double k) { double result = 1; for (int i = 1; i < k + 1; i++) { result *= (n - i + 1) / i; } return result; }
public static void main(String[] args) { System.out.println(binomCoeff(5, 3)); }
} </lang>
- Output:
10.0
Recursive version:
<lang java>public class Binomial {
private static long binom(int n, int k) { if (k==0) return 1; else if (k>n-k) return binom(n, n-k); else return binom(n-1, k-1)*n/k; }
public static void main(String[] args) { System.out.println(binom(5, 3)); }
}</lang>
- Output:
10
JavaScript
<lang javascript>function binom(n, k) {
var coeff = 1; for (var i = n-k+1; i <= n; i++) coeff *= i; for (var i = 1; i <= k; i++) coeff /= i; return coeff;
} print(binom(5,3));</lang>
10
jq
<lang jq># nCk assuming n >= k def binomial(n; k):
if k > n / 2 then binomial(n; n-k) else reduce range(1; k+1) as $i (1; . * (n - $i + 1) / $i) end;
def task:
.[0] as $n | .[1] as $k | "\($n) C \($k) = \(binomial( $n; $k) )";
([5,3], [100,2], [ 33,17]) | task </lang>
- Output:
5 C 3 = 10 100 C 2 = 4950 33 C 17 = 1166803110
Julia
Built-in (uses gamma
function):
<lang julia>@show binomial(5, 3)</lang>
Recursive version: <lang julia>function binom(n::Integer, k::Integer)
n ≥ k || return 0 # short circuit base cases n == 1 || k == 0 && return 1
return (n * binom(n - 1, k - 1)) ÷ k
end
@show binom(5, 3)</lang>
- Output:
binomial(5, 3) = 10 binom(5, 3) = 10
K
<lang K> {[n;k]_(*/(k-1)_1+!n)%(*/1+!k)} . 5 3 10</lang>
Alternative version: <lang K> {[n;k]i:!(k-1);_*/((n-i)%(i+1))} . 5 3 10</lang>
Using Pascal's triangle: <lang K> pascal:{x{+':0,x,0}\1}
pascal 5
(1
1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1)
{[n;k](pascal n)[n;k]} . 5 3
10</lang>
Kotlin
<lang scala>// version 1.0.5-2
fun factorial(n: Int) = when {
n < 0 -> throw IllegalArgumentException("negative numbers not allowed") else -> { var ans = 1L for (i in 2..n) ans *= i ans }
}
fun binomial(n: Int, k: Int) = when {
n < 0 || k < 0 -> throw IllegalArgumentException("negative numbers not allowed") n == k -> 1L else -> { var ans = 1L for (i in n - k + 1..n) ans *= i ans / factorial(k) }
}
fun main(args: Array<String>) {
for (n in 0..14) { for (k in 0..n) print("%4d ".format(binomial(n, k))) println() }
}</lang>
- Output:
1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1 1 9 36 84 126 126 84 36 9 1 1 10 45 120 210 252 210 120 45 10 1 1 11 55 165 330 462 462 330 165 55 11 1 1 12 66 220 495 792 924 792 495 220 66 12 1 1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1 1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1
Lasso
<lang Lasso>define binomial(n::integer,k::integer) => { #k == 0 ? return 1 local(result = 1) loop(#k) => { #result = #result * (#n - loop_count + 1) / loop_count } return #result } // Tests binomial(5, 3) binomial(5, 4) binomial(60, 30)</lang>
- Output:
10 5 118264581564861424
Logo
<lang logo>to choose :n :k
if :k = 0 [output 1] output (choose :n :k-1) * (:n - :k + 1) / :k
end
show choose 5 3 ; 10 show choose 60 30 ; 1.18264581564861e+17</lang>
Lua
<lang lua>function Binomial( n, k )
if k > n then return nil end if k > n/2 then k = n - k end -- (n k) = (n n-k) numer, denom = 1, 1 for i = 1, k do numer = numer * ( n - i + 1 ) denom = denom * i end return numer / denom
end</lang>
Additive recursion with memoization by hashing 2 input integer. Lua 5.3 support bit-wise operation; assume 64 bit integer implementation here. <lang lua>local Binomial = setmetatable({},{
__call = function(self,n,k) local hash = (n<<32) | (k & 0xffffffff) local ans = self[hash] if not ans then if n<0 or k>n then return 0 -- not save elseif n<=1 or k==0 or k==n then ans = 1 else if 2*k > n then ans = self(n, n - k) else local lhs = self(n-1,k) local rhs = self(n-1,k-1) local sum = lhs + rhs if sum<0 or not math.tointeger(sum)then -- switch to double ans = lhs/1.0 + rhs/1.0 -- approximate else ans = sum end end end rawset(self,hash,ans) end return ans end
}) print( Binomial(100,50)) -- 1.0089134454556e+029 </lang>
Liberty BASIC
<lang lb>
' [RC] Binomial Coefficients
print "Binomial Coefficient of "; 5; " and "; 3; " is ",BinomialCoefficient( 5, 3) n =1 +int( 10 *rnd( 1)) k =1 +int( n *rnd( 1)) print "Binomial Coefficient of "; n; " and "; k; " is ",BinomialCoefficient( n, k)
end
function BinomialCoefficient( n, k) BinomialCoefficient =factorial( n) /factorial( n -k) /factorial( k) end function
function factorial( n) if n <2 then f =1 else f =n *factorial( n -1) end if factorial =f end function </lang>
Maple
<lang Maple>convert(binomial(n,k),factorial);
binomial(5,3);</lang>
- Output:
factorial(n) ----------------------------- factorial(k) factorial(n - k) 10
Mathematica / Wolfram Language
<lang Mathematica>(Local) In[1]:= Binomial[5,3] (Local) Out[1]= 10</lang>
MATLAB / Octave
This is a built-in function in MATLAB called "nchoosek(n,k)". But, this will only work for scalar inputs. If "n" is a vector then "nchoosek(v,k)" finds all combinations of choosing "k" elements out of the "v" vector (see Combinations#MATLAB).
Solution: <lang MATLAB>>> nchoosek(5,3) ans =
10</lang>
Alternative implementations are:
<lang MATLAB>function r = binomcoeff1(n,k)
r = diag(rot90(pascal(n+1))); % vector of all binomial coefficients for order n r = r(k);
end; </lang>
<lang MATLAB>function r = binomcoeff2(n,k)
prod((n-k+1:n)./(1:k))
end; </lang>
<lang MATLAB>function r = binomcoeff3(n,k)
m = pascal(max(n-k,k)+1); r = m(n-k+1,k+1);
end; </lang>
If you want a vectorized function that returns multiple binomial coefficients given vector inputs, you must define that function yourself. A sample implementation is given below. This function takes either scalar or vector inputs for "n" and "v" and returns either a: scalar, vector, or matrix. Where the columns are indexed by the "k" vector and the rows indexed by the "n" vector. binomialCoeff.m: <lang MATLAB>function coefficients = binomialCoeff(n,k)
coefficients = zeros(numel(n),numel(k)); %Preallocate memory
columns = (1:numel(k)); %Preallocate row and column counters rows = (1:numel(n)); %Iterate over every row and column. The rows represent the n number, %and the columns represent the k number. If n is ever greater than k, %the nchoosek function will throw an error. So, we test to make sure %it isn't, if it is then we leave that entry in the coefficients matrix %zero. Which makes sense combinatorically. for row = rows for col = columns if k(col) <= n(row) coefficients(row,col) = nchoosek(n(row),k(col)); end end end
end %binomialCoeff</lang> Sample Usage: <lang MATLAB>>> binomialCoeff((0:5),(0:5))
ans =
1 0 0 0 0 0 1 1 0 0 0 0 1 2 1 0 0 0 1 3 3 1 0 0 1 4 6 4 1 0 1 5 10 10 5 1
>> binomialCoeff([1 0 3 2],(0:3))
ans =
1 1 0 0 1 0 0 0 1 3 3 1 1 2 1 0
>> binomialCoeff(3,(0:3))
ans =
1 3 3 1
>> binomialCoeff((0:3),2)
ans =
0 0 1 3
>> binomialCoeff(5,3)
ans =
10</lang>
Maxima
<lang maxima>binomial( 5, 3); /* 10 */ binomial(-5, 3); /* -35 */ binomial( 5, -3); /* 0 */ binomial(-5, -3); /* 0 */ binomial( 3, 5); /* 0 */
binomial(x, 3); /* ((x - 2)*(x - 1)*x)/6 */
binomial(3, 1/2); /* binomial(3, 1/2) */ makegamma(%); /* 32/(5*%pi) */
binomial(a, b); /* binomial(a, b) */ makegamma(%); /* gamma(a + 1)/(gamma(-b + a + 1)*gamma(b + 1)) */</lang>
МК-61/52
<lang>П1 <-> П0 ПП 22 П2 ИП1 ПП 22 П3 ИП0 ИП1 - ПП 22 ИП3 * П3 ИП2 ИП3 / С/П ВП П0 1 ИП0 * L0 25 В/О</lang>
Input: n ^ k В/О С/П.
MINIL
<lang minil>// Number of combinations nCr 00 0E Go: ENT R0 // n 01 1E ENT R1 // r 02 2C CLR R2 03 2A Loop: ADD1 R2 04 0D DEC R0 05 1D DEC R1 06 C3 JNZ Loop 07 3C CLR R3 // for result 08 3A ADD1 R3 09 0A Next: ADD1 R0 0A 1A ADD1 R1 0B 50 R5 = R0 0C 5D DEC R5 0D 63 R6 = R3 0E 46 Mult: R4 = R6 0F 3A Add: ADD1 R3 10 4D DEC R4 11 CF JNZ Add 12 5D DEC R5 13 CE JNZ Mult 14 61 Divide:R6 = R1 15 5A ADD1 R5 16 3D Sub: DEC R3 17 9B JZ Exact 18 6D DEC R6 19 D6 JNZ Sub 1A 94 JZ Divide 1B 35 Exact: R3 = R5 1C 2D DEC R2 1D C9 JNZ Next 1E 03 R0 = R3 1F 80 JZ Go // Display result</lang>
This uses the recursive definition:
ncr(n, r) = 1 if r = 0
ncr(n, r) = n/r * ncr(n-1, r-1) otherwise
which results from the definition of ncr in terms of factorials.
Nim
<lang nim>proc binomialCoeff(n, k: int): int =
result = 1 for i in 1..k: result = result * (n-i+1) div i
echo binomialCoeff(5, 3)</lang>
- Output:
10
Oberon
<lang oberon2> MODULE Binomial; IMPORT
Out;
PROCEDURE For*(n,k: LONGINT): LONGINT; VAR
i,m,r: LONGINT;
BEGIN
ASSERT(n > k); r := 1; IF k > n DIV 2 THEN m := n - k ELSE m := k END; FOR i := 1 TO m DO r := r * (n - m + i) DIV i END; RETURN r
END For;
BEGIN
Out.Int(For(5,2),0);Out.Ln
END Binomial. </lang>
- Output:
10
OCaml
<lang OCaml> let binomialCoeff n p =
let p = if p < n -. p then p else n -. p in let rec cm res num denum = (* this method partially prevents overflow. * float type is choosen to have increased domain on 32-bits computer, * however algorithm ensures an integral result as long as it is possible *) if denum <= p then cm ((res *. num) /. denum) (num -. 1.) (denum +. 1.) else res in cm 1. n 1.
</lang>
Alternate version using big integers
<lang ocaml>#load "nums.cma";; open Num;;
let binomial n p =
let m = min p (n - p) in if m < 0 then Int 0 else let rec a j v = if j = m then v else a (succ j) ((v */ (Int (n - j))) // (Int (succ j))) in a 0 (Int 1)
- </lang>
Simple recursive version
<lang OCaml>open Num;; let rec binomial n k = if n = k then Int 1 else ((binomial (n-1) k) */ Int n) // Int (n-k)</lang>
Oforth
<lang Oforth>: binomial(n, k) | i | 1 k loop: i [ n i - 1+ * i / ] ;</lang>
- Output:
>5 3 binomial . 10
Oz
<lang oz>declare
fun {BinomialCoeff N K} {List.foldL {List.number 1 K 1} fun {$ Z I} Z * (N-I+1) div I end 1} end
in
{Show {BinomialCoeff 5 3}}</lang>
PARI/GP
<lang parigp>binomial(5,3)</lang>
Pascal
See Delphi
Perl
<lang perl>sub binomial {
use bigint; my ($r, $n, $k) = (1, @_); for (1 .. $k) { $r *= $n--; $r /= $_ } $r;
}
print binomial(5, 3);</lang>
- Output:
10
Since the bigint module already has a binomial method, this could also be written as: <lang perl>sub binomial {
use bigint; my($n,$k) = @_; (0+$n)->bnok($k);
}</lang>
For better performance, especially with large inputs, one can also use something like:
<lang perl>use ntheory qw/binomial/; print length(binomial(100000,50000)), "\n";</lang>
- Output:
30101
The Math::Pari module also has binomial, but it needs large amounts of added stack space for large arguments (this is due to using a very old version of the underlying Pari library).
Perl 6
For a start, you can get the length of the corresponding list of combinations: <lang perl6>say combinations(5, 3).elems;</lang>
- Output:
10
This method is efficient, as Perl 6 will not actually compute each element of the list, since it actually uses an iterator with a defined count-only method. Such method performs computations in a way similar to the following infix operator:
<lang perl6>sub infix:<choose> { [*] ($^n ... 0) Z/ 1 .. $^p } say 5 choose 3;</lang>
A possible optimization would use a symmetry property of the binomial coefficient:
<lang perl6>sub infix:<choose> { [*] ($^n ... 0) Z/ 1 .. min($n - $^p, $p) }</lang>
One drawback of this method is that it returns a Rat, not an Int. So we actually may want to enforce the conversion: <lang perl6>sub infix:<choose> { ([*] ($^n ... 0) Z/ 1 .. min($n - $^p, $p)).Int }</lang>
And this is exactly what the count-only method does.
Phix
A naive version: <lang Phix>function binom(integer n, k)
return factorial(n)/(factorial(k)*factorial(n-k))
end function
?binom(5,3)</lang>
- Output:
10
However errors will creep in should any result or interim value exceed 9,007,199,254,740,992 (on 32-bit), so (and using a different algorithm just for kicks):
<lang Phix>include builtins\bigatom.e
function ba_binom(integer n, k) bigatom r = ba_new(1)
for i=1 to k do r = ba_divide(ba_multiply(r,n-i+1),i) end for return r
end function
?ba_sprintf("%B",ba_binom(5,3)) ?ba_sprintf("%B",ba_binom(100,50)) ?ba_sprintf("%B",ba_binom(60,30)) ?ba_sprintf("%B",ba_binom(1200,120))</lang>
- Output:
"10" "100891344545564193334812497256" "118264581564861424" "1004576581793084916475353119318331966507299414258370667602185866686463289093457468590558508056798211449853806741873396451735444387513582540860551330127062642417424083600"
PHP
<lang PHP><?php $n=5; $k=3; function factorial($val){
for($f=2;$val-1>1;$f*=$val--); return $f;
} $binomial_coefficient=factorial($n)/(factorial($k)*factorial($n-$k)); echo $binomial_coefficient; ?></lang>
Alternative version, not based on factorial <lang PHP> function binomial_coefficient($n, $k) {
if ($k == 0) return 1; $result = 1; foreach (range(0, $k - 1) as $i) { $result *= ($n - $i) / ($i + 1); } return $result;
} </lang>
PicoLisp
<lang PicoLisp>(de binomial (N K)
(let f '((N) (if (=0 N) 1 (apply * (range 1 N))) ) (/ (f N) (* (f (- N K)) (f K)) ) ) )</lang>
- Output:
: (binomial 5 3) -> 10
PL/I
<lang PL/I> binomial_coefficients:
procedure options (main); declare (n, k) fixed;
get (n, k); put (coefficient(n, k));
coefficient: procedure (n, k) returns (fixed decimal (15));
declare (n, k) fixed; return (fact(n)/ (fact(n-k) * fact(k)) );
end coefficient;
fact: procedure (n) returns (fixed decimal (15));
declare n fixed; declare i fixed, f fixed decimal (15); f = 1; do i = 1 to n; f = f * i; end; return (f);
end fact; end binomial_coefficients; </lang>
- Output:
10
PowerShell
<lang PowerShell> function choose($n,$k) {
if($k -le $n -and 0 -le $k) { $numerator = $denominator = 1 0..($k-1) | foreach{ $numerator *= ($n-$_) $denominator *= ($_ + 1) } $numerator/$denominator } else { "$k is greater than $n or lower than 0" }
} choose 5 3 choose 2 1 choose 10 10 choose 10 2 choose 10 8 </lang> Output:
10 2 1 45 45
PureBasic
<lang PureBasic>Procedure Factor(n)
Protected Result=1 While n>0 Result*n n-1 Wend ProcedureReturn Result
EndProcedure
Macro C(n,k)
(Factor(n)/(Factor(k)*factor(n-k)))
EndMacro
If OpenConsole()
Print("Enter value n: "): n=Val(Input()) Print("Enter value k: "): k=Val(Input()) PrintN("C(n,k)= "+str(C(n,k))) Print("Press ENTER to quit"): Input() CloseConsole()
EndIf</lang> Example
Enter value n: 5 Enter value k: 3 C(n,k)= 10
Python
Imperative
<lang python>def binomialCoeff(n, k):
result = 1 for i in range(1, k+1): result = result * (n-i+1) / i return result
if __name__ == "__main__":
print(binomialCoeff(5, 3))</lang>
- Output:
10
Functional
<lang python>from operator import mul def comb(n,r):
calculate nCr - the binomial coefficient >>> comb(3,2) 3 >>> comb(9,4) 126 >>> comb(9,6) 84 >>> comb(20,14) 38760 if r > n-r: # for smaller intermediate values r = n-r return int( reduce( mul, range((n-r+1), n+1), 1) / reduce( mul, range(1,r+1), 1) )</lang>
R
R's built-in choose() function evaluates binomial coefficients: <lang r>choose(5,3)</lang>
- Output:
[1] 10
Racket
<lang racket>
- lang racket
(require math) (binomial 10 5) </lang>
REXX
The task is to compute ANY binomial coefficient(s), but these REXX examples are limited to 100k digits.
idiomatic
<lang rexx>/*REXX program calculates binomial coefficients (also known as combinations). */ numeric digits 100000 /*be able to handle gihugeic numbers. */ parse arg n k . /*obtain N and K from the C.L. */ say 'combinations('n","k')=' comb(n,k) /*display the number of combinations. */ exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ comb: procedure; parse arg x,y; return !(x) % (!(x-y) * !(y)) !: procedure; !=1; do j=2 to arg(1); !=!*j; end /*j*/; return !</lang> output when using the input of: 5 3
combinations(5,3)= 10
output when using the input of: 1200 120
combinations(1200,120)= 1004576581793084916475353119318331966507299414258370667602185866686463289093457468590558508056798211449853806741873396451735444387513582540860551330127062642417424083600
optimized
This REXX version takes advantage of reducing the size (product) of the numerator, and also,
only two (factorial) products need be calculated.
<lang rexx>/*REXX program calculates binomial coefficients (also known as combinations). */
numeric digits 100000 /*be able to handle gihugeic numbers. */
parse arg n k . /*obtain N and K from the C.L. */
say 'combinations('n","k')=' comb(n,k) /*display the number of combinations. */
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
comb: procedure; parse arg x,y; return pfact(x-y+1, x) % pfact(2, y)
/*──────────────────────────────────────────────────────────────────────────────────────*/
pfact: procedure; !=1; do j=arg(1) to arg(2); !=!*j; end /*j*/; return !</lang>
output is identical to the 1st REXX version.
It is (around average) about ten times faster than the 1st version for 200,20
and 100,10
.
For 100,80
it is about 30% faster.
Ring
<lang ring> numer = 0 binomial(5,3) see "(5,3) binomial = " + numer + nl
func binomial n, k
if k > n return nil ok if k > n/2 k = n - k ok numer = 1 for i = 1 to k numer = numer * ( n - i + 1 ) / i next return numer
</lang>
Ruby
<lang ruby>class Integer
# binomial coefficient: n C k def choose(k) # n!/(n-k)! pTop = (self-k+1 .. self).inject(1, &:*) # k! pBottom = (2 .. k).inject(1, &:*) pTop / pBottom end
end
p 5.choose(3) p 60.choose(30)</lang> result
10 118264581564861424
another implementation:
<lang ruby> def c n, r
(0...r).inject(1) do |m,i| (m * (n - i)) / (i + 1) end
end </lang>Ruby's Arrays have a combination method which result in a (lazy) enumerator. This Enumerator has a "size" method, which returns the size of the enumerator, or nil if it can’t be calculated lazily. (Since Ruby 2.0) <lang ruby>(1..60).to_a.combination(30).size #=> 118264581564861424</lang>
Run BASIC
<lang runbasic>print "binomial (5,1) = "; binomial(5, 1) print "binomial (5,2) = "; binomial(5, 2) print "binomial (5,3) = "; binomial(5, 3) print "binomial (5,4) = "; binomial(5,4) print "binomial (5,5) = "; binomial(5,5) end
function binomial(n,k)
coeff = 1 for i = n - k + 1 to n coeff = coeff * i next i for i = 1 to k coeff = coeff / i next i
binomial = coeff end function</lang>
- Output:
binomial (5,1) = 5 binomial (5,2) = 10 binomial (5,3) = 10 binomial (5,4) = 5 binomial (5,5) = 1
Rust
<lang rust>fn fact(n:u32) -> u64 {
let mut f:u64 = n as u64; for i in 2..n { f *= i as u64; } return f;
}
fn choose(n: u32, k: u32) -> u64 {
let mut num:u64 = n as u64; for i in 1..k { num *= (n-i) as u64; } return num / fact(k);
}
fn main() {
println!("{}", choose(5,3));
}</lang>
- Output:
10
Scala
<lang scala>object Binomial {
def main(args: Array[String]): Unit = { val n=5 val k=3 val result=binomialCoefficient(n,k) println("The Binomial Coefficient of %d and %d equals %d.".format(n, k, result)) }
def binomialCoefficient(n:Int, k:Int)=fact(n) / (fact(k) * fact(n-k)) def fact(n:Int):Int=if (n==0) 1 else n*fact(n-1)
}</lang>
- Output:
The Binomial Coefficient of 5 and 3 equals 10.
Another (more flexible and efficient) implementation. n and k are taken from command line. The use of BigInts allows to compute coefficients of arbitrary size:
<lang scala>object Binomial extends App {
def binomialCoefficient(n: Int, k: Int) = (BigInt(n - k + 1) to n).product / (BigInt(1) to k).product
val Array(n, k) = args.map(_.toInt) println("The Binomial Coefficient of %d and %d equals %,3d.".format(n, k, binomialCoefficient(n, k)))
}</lang>
- Output:
java Binomial 100 30 The Binomial Coefficient of 100 and 30 equals 29,372,339,821,610,944,823,963,760.
Using recursive formula C(n,k) = C(n-1,k-1) + C(n-1,k)
:
<lang scala> def bico(n: Long, k: Long): Long = (n, k) match {
case (n, 0) => 1 case (0, k) => 0 case (n, k) => bico(n - 1, k - 1) + bico(n - 1, k) } println("bico(5,3) = " + bico(5, 3))</lang>
- Output:
bico(5,3) = 10
Scheme
<lang scheme>(define (factorial n)
(define (*factorial n acc) (if (zero? n) acc (*factorial (- n 1) (* acc n)))) (*factorial n 1))
(define (choose n k)
(/ (factorial n) (* (factorial k) (factorial (- n k)))))
(display (choose 5 3)) (newline)</lang>
- Output:
10
Seed7
The infix operator ! computes the binomial coefficient. E.g.: 5 ! 3 evaluates to 10. The binomial coefficient operator works also for negative values of n. E.g.: (-6) ! 10 evaluates to 3003.
<lang seed7>$ include "seed7_05.s7i";
const proc: main is func
local var integer: n is 0; var integer: k is 0; begin for n range 0 to 66 do for k range 0 to n do write(n ! k <& " "); end for; writeln; end for; end func;</lang>
- Output:
1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1 1 9 36 84 126 126 84 36 9 1 1 10 45 120 210 252 210 120 45 10 1 1 11 55 165 330 462 462 330 165 55 11 1 1 12 66 220 495 792 924 792 495 220 66 12 1 1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1 1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1 1 15 105 455 1365 3003 5005 6435 6435 5005 3003 1365 455 105 15 1 1 16 120 560 1820 4368 8008 11440 12870 11440 8008 4368 1820 560 120 16 1 1 17 136 680 2380 6188 12376 19448 24310 24310 19448 12376 6188 2380 680 136 17 1 1 18 153 816 3060 8568 18564 31824 43758 48620 43758 31824 18564 8568 3060 816 153 18 1 1 19 171 969 3876 11628 27132 50388 75582 92378 92378 75582 50388 27132 11628 3876 969 171 19 1 1 20 190 1140 4845 15504 38760 77520 125970 167960 184756 167960 125970 77520 38760 15504 4845 1140 190 20 1 ...
The library bigint.s7i contains a definition of the binomial coefficient operator ! for the type bigInteger:
<lang seed7>const func bigInteger: (in bigInteger: n) ! (in var bigInteger: k) is func
result var bigInteger: binom is 0_; local var bigInteger: numerator is 0_; var bigInteger: denominator is 0_; begin if n >= 0_ and k > n >> 1 then k := n - k; end if; if k < 0_ then binom := 0_; elsif k = 0_ then binom := 1_; else binom := n; numerator := pred(n); denominator := 2_; while denominator <= k do binom *:= numerator; binom := binom div denominator; decr(numerator); incr(denominator); end while; end if; end func;
</lang>
Original source [1].
SequenceL
Simplest Solution: <lang sequenceL> choose(n, k) := product(k + 1 ... n) / product(1 ... n - k); </lang>
Tail-Recursive solution to avoid arithmetic with large integers: <lang sequenceL>
choose(n,k) := binomial(n, k, 1, 1);
binomial(n, k, i, result) := result when i > k else binomial(n, k, i + 1, (result * (n - i + 1)) / i); </lang>
Sidef
Straightforward translation of the formula: <lang ruby>func binomial(n,k) {
n! / ((n-k)! * k!)
}
say binomial(400, 200)</lang>
Alternatively, by using the Number.nok() method: <lang ruby>say 400.nok(200)</lang>
Stata
Use the comb function. Notice the result is a missing value if k>n or k<0.
<lang stata>. display comb(5,3) 10</lang>
Tcl
This uses exact arbitrary precision integer arithmetic. <lang tcl>package require Tcl 8.5 proc binom {n k} {
# Compute the top half of the division; this is n!/(n-k)! set pTop 1 for {set i $n} {$i > $n - $k} {incr i -1} {
set pTop [expr {$pTop * $i}]
}
# Compute the bottom half of the division; this is k! set pBottom 1 for {set i $k} {$i > 1} {incr i -1} {
set pBottom [expr {$pBottom * $i}]
}
# Integer arithmetic divide is correct here; the factors always cancel out return [expr {$pTop / $pBottom}]
}</lang> Demonstrating: <lang tcl>puts "5_C_3 = [binom 5 3]" puts "60_C_30 = [binom 60 30]"</lang>
- Output:
5_C_3 = 10 60_C_30 = 118264581564861424
TI-83 BASIC
Builtin operator nCr gives the number of combinations. <lang ti83b>10 nCr 4</lang>
- Output:
210
TI-89 BASIC
Builtin function.
<lang ti89b>nCr(n,k)</lang>
TXR
nCk is a built-in function, along with the one for permutations, nPk:
<lang sh>$ txr -p '(n-choose-k 20 15)' 15504</lang>
<lang sh>$ txr -p '(n-perm-k 20 15)' 20274183401472000</lang>
UNIX Shell
<lang sh>#!/bin/sh n=5; k=3; calculate_factorial(){ partial_factorial=1; for (( i=1; i<="$1"; i++ )) do
factorial=$(expr $i \* $partial_factorial) partial_factorial=$factorial
done echo $factorial }
n_factorial=$(calculate_factorial $n) k_factorial=$(calculate_factorial $k) n_minus_k_factorial=$(calculate_factorial `expr $n - $k`) binomial_coefficient=$(expr $n_factorial \/ $k_factorial \* 1 \/ $n_minus_k_factorial )
echo "Binomial Coefficient ($n,$k) = $binomial_coefficient"</lang>
Ursala
A function for computing binomial coefficients (choose
) is included in a standard library, but if it weren't, it could be defined in one of the following ways, starting from the most idiomatic.
<lang Ursala>#import nat
choose = ~&ar^?\1! quotient^\~&ar product^/~&al ^|R/~& predecessor~~</lang>
The standard library functions quotient
, product
and predecessor
pertain to natural numbers in the obvious way.
choose
is defined using the recursive conditional combinator (^?
) as a function taking a pair of numbers, with the predicate~&ar
testing whether the number on the right side of the pair is non-zero.- If the predicate does not hold (implying the right side is zero), then a constant value of 1 is returned.
- If the predicate holds, the function given by the rest of the expression executes as follows.
- First the
predecessor
of both sides (~~
) of the argument is taken. - Then a recursive call (
^|R
) is made to the whole function (~&
) with the pair of predecessors passed to it as an argument. - The result returned by the recursive call is multiplied (
product
) by the left side of the original argument (~&al
). - The product of these values is then divided (
quotient
) by the right side (~&ar
) of the original argument and returned as the result.
Here is a less efficient implementation more closely following the formula above. <lang Ursala>choose = quotient^/factorial@l product+ factorial^~/difference ~&r</lang>
choose
is defined as thequotient
of the results of a pair (^
) of functions.- The left function contributing to the quotient is the
factorial
of the left side (@l
) of the argument, which is assumed to be a pair of natural numbers. Thefactorial
function is provided in a standard library. - The right function contributing to the quotient is the function given by the rest of the expression, which applies to the whole pair as follows.
- It begins by forming a pair of numbers from the argument, the left being their
difference
obtained by subtraction, and the right being the a copy of the right (~&r
) side of the argument. - The
factorial
function is applied separately to both results (^~
). - A composition (
+
) of this function with theproduct
function effects the multiplication of the two factorials, to complete the other input to the quotient.
Here is an equivalent implementation using pattern matching, dummy variables, and only the apply-to-both (~~
) operator.
<lang Ursala>choose("n","k") = quotient(factorial "n",product factorial~~ (difference("n","k"),"k"))</lang>
test program:
<lang Ursala>#cast %nL
main = choose* <(5,3),(60,30)></lang>
- Output:
<10,118264581564861424>
VBScript
<lang vb>Function binomial(n,k) binomial = factorial(n)/(factorial(n-k)*factorial(k)) End Function
Function factorial(n) If n = 0 Then factorial = 1 Else For i = n To 1 Step -1 If i = n Then factorial = n Else factorial = factorial * i End If Next End If End Function
'calling the function WScript.StdOut.Write "the binomial coefficient of 5 and 3 = " & binomial(5,3) WScript.StdOut.WriteLine</lang>
- Output:
the binomial coefficient of 5 and 3 = 10
XPL0
<lang XPL0>code ChOut=8, CrLf=9, IntOut=11;
func Binomial(N, K); int N, K; int M, B, I; [M:= K; if K>N/2 the M:= N-K; B:=1; for I:= 1 to M do
B:= B*(N-M+I)/I;
return B; ];
int N, K; [for N:= 0 to 9 do
[for K:= 0 to 9 do [if N>=K then IntOut(0, Binomial(N,K)); ChOut(0, 9\tab\); ]; CrLf(0); ];
] \Mr. Pascal's triangle!</lang>
- Output:
1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1 1 9 36 84 126 126 84 36 9 1
zkl
Using 64 bit ints: <lang zkl>fcn binomial(n,k){ (1).reduce(k,fcn(p,i,n){ p*(n-i+1)/i },1,n) }</lang>
- Output:
zkl: binomial(5,3) 10 zkl: binomial(60,30) 118264581564861424
ZX Spectrum Basic
<lang zxbasic>10 LET n=33: LET k=17: PRINT "Binomial ";n;",";k;" = "; 20 LET r=1: LET d=n-k 30 IF d>k THEN LET k=d: LET d=n-k 40 IF n<=k THEN GO TO 90 50 LET r=r*n 60 LET n=n-1 70 IF (d>1) AND (FN m(r,d)=0) THEN LET r=r/d: LET d=d-1: GO TO 70 80 GO TO 40 90 PRINT r 100 DEF FN m(a,b)=a-INT (a/b)*b</lang>
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