Loops/Nested
You are encouraged to solve this task according to the task description, using any language you may know.
Show a nested loop which searches two-dimensional array filled with random number uniformly distributed on [1..20]. The loops iterate rows and columns of the array printing the iterated elements of, until the value 20 is met.
Ada
<lang ada> with Ada.Text_IO; use Ada.Text_IO; with Ada.Numerics.Discrete_Random;
procedure Test_Loop_Nested is
type Value_Type is range 1..20;
package Random_Values is new Ada.Numerics.Discrete_Random (Value_Type);
use Random_Values;
Dice : Generator;
A : array (1..10, 1..10) of Value_Type :=
(others => (others => Random (Dice)));
begin
Outer :
for I in A'Range (1) loop
for J in A'Range (2) loop
Put (Value_Type'Image (A (I, J)));
exit Outer when A (I, J) = 20;
end loop;
New_Line;
end loop Outer;
end Test_Loop_Nested; </lang> Sample output:
16 3 1 17 13 5 4 2 19 1 5 5 17 15 17 2 5 5 17 13 16 10 10 20
AutoHotkey
<lang AutoHotkey>Loop, 10 {
i := A_Index
Loop, 10
{
j := A_Index
Random, a%i%%j%, 1, 20
}
}
Loop, 10 {
i := A_Index
Loop, 10
{
j := A_Index
If (a%i%%j% == 20)
Goto finish
}
}
finish:
MsgBox % "a[" . i . "][" . j . "]" is 20
Return</lang>
BASIC
<lang qbasic>DIM a(1 TO 10, 1 TO 10) AS INTEGER CLS FOR row = 1 TO 10
FOR col = 1 TO 10
a(row, col) = INT(RND * 20) + 1
NEXT col
NEXT row
FOR row = LBOUND(a, 1) TO UBOUND(a, 1)
FOR col = LBOUND(a, 2) TO UBOUND(a, 2)
PRINT a(row, col)
IF a(row, col) = 20 THEN END
NEXT col
NEXT row</lang>
C
Using goto (note: gotos are considered harmful): <lang c>#include <stdlib.h>
- include <time.h>
- include <stdio.h>
int main() {
int a[10][10], i, j;
srand(time(NULL));
for (i = 0; i < 10; i++)
for (j = 0; j < 10; j++)
a[i][j] = rand() % 20 + 1;
for (i = 0; i < 10; i++) {
for (j = 0; j < 10; j++) {
printf(" %d", a[i][j]);
if (a[i][j] == 20)
goto Done;
}
printf("\n");
}
Done:
printf("\n");
return 0;
}</lang>
Common Lisp
<lang lisp>(let ((a (make-array '(10 10))))
(dotimes (i 10)
(dotimes (j 10)
(setf (aref a i j) (1+ (random 20)))))
(block outer
(dotimes (i 10)
(dotimes (j 10)
(princ " ")
(princ (aref a i j))
(if (= 20 (aref a i j))
(return-from outer)))
(terpri))
(terpri)))</lang>
D
<lang d>import std.stdio, std.random;
void main() {
int[10][10] m;
foreach (ref row; m)
foreach (ref item; row)
item = rand % 20 + 1;
outer:
foreach (row; m)
foreach (item; row) {
writef(item, ' ');
if (item == 20)
break outer;
}
writefln;
}</lang>
E
<lang e>def array := accum [] for i in 1..5 { _.with(accum [] for i in 1..5 { _.with(entropy.nextInt(20) + 1) }) }
escape done {
for row in array {
for x in row {
print(`$x$\t`)
if (x == 20) {
done()
}
}
println()
}
} println("done.")</lang>
Forth
<lang forth> include random.fs
10 constant X 10 constant Y
- ,randoms ( range n -- ) 0 do dup random 1+ , loop drop ;
create 2darray 20 X Y * ,randoms
- main
Y 0 do
cr
X 0 do
j X * i + cells 2darray + @
dup .
20 = if unloop unloop exit then
loop
loop ;
</lang>
Fortran
<lang fortran> program Example
implicit none
real :: ra(5,10) integer :: ia(5,10) integer :: i, j
call random_number(ra) ia = int(ra * 20.0) + 1
outer: do i = 1, size(ia, 1)
do j = 1, size(ia, 2)
write(*, "(i3)", advance="no") ia(i,j)
if (ia(i,j) == 20) exit outer
end do
write(*,*)
end do outer
end program Example </lang> Sample output:
14 2 1 11 8 1 14 11 3 15 7 15 16 6 7 17 3 20
Java
<lang java>import java.util.Random;
public class NestedLoopTest {
public static final Random gen = new Random();
public static void main(String[] args) {
int[][] a = new int[10][10];
for (int i = 0; i < a.length; i++)
for (int j = 0; j < a[i].length; j++)
a[i][j] = gen.nextInt(20) + 1;
Outer:
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
System.out.print(" " + a[i][j]);
if (a[i][j] == 20)
break Outer;
}
System.out.println();
}
System.out.println();
}
}</lang>
Logo
<lang logo> make "a mdarray [10 10]
for [j 1 10] [for [i 1 10] [mdsetitem list :i :j :a (1 + random 20)]]
to until.20
for [j 1 10] [
for [i 1 10] [
type mditem list :i :j :a
type "| |
if equal? 20 mditem list :i :j :a [stop]
]
print "||
]
end until.20 </lang>
MOO
<lang moo> a = make(10, make(10)); for i in [1..10]
for j in [1..10] a[i][j] = random(20); endfor
endfor for i in [1..10]
s = "";
for j in [1..10]
s += tostr(" ", a[i][j]);
if (a[i][j] == 20)
break i;
endif
endfor
player:tell(s);
s = "";
endfor player:tell(s);</lang>
OCaml
<lang ocaml># Random.self_init();; - : unit = ()
- let m = Array.make_matrix 10 10 0 ;;
val m : int array array =
[|[|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]; [|0; 0; 0; 0; 0; 0; 0; 0; 0; 0|]|]
- for i = 0 to pred 10 do
for j = 0 to pred 10 do
m.(i).(j) <- 1 + Random.int 20
done;
done;;
- : unit = ()
- try
for i = 0 to pred 10 do
for j = 0 to pred 10 do
Printf.printf " %d" m.(i).(j);
if m.(i).(j) = 20 then raise Exit;
done;
print_newline()
done;
with Exit ->
print_newline()
;;
15 8 15 9 9 6 1 18 6 18
17 1 13 15 13 1 16 4 13 9
15 3 5 19 17 3 1 11 5 2
1 1 6 19 20
- : unit = ()</lang>
Octave
Octave has no way of exiting nested loop; so we need a control variable, or we can use the trick of embedding the loops into a function and use the return statement. (The search for "exactly 20" is changed into a search for "almost 20")
<lang octave>function search_almost_twenty() % create a 100x100 matrix... m = unifrnd(0,20, 100,100); for i = 1:100
for j = 1:100
disp( m(i,j) )
if ( abs(m(i,j) - 20) < 1e-2 )
return
endif
endfor
endfor endfunction
search_almost_twenty()
% avoiding function, we need a control variable. m = unifrnd(0,20, 100,100); innerloopbreak = false; for i = 1:100
for j = 1:100
disp( m(i,j) )
if ( abs(m(i,j) - 20) < 1e-2 )
innerloopbreak = true;
break;
endif
endfor
if ( innerloopbreak )
break;
endif
endfor</lang>
Perl
<lang perl>my $a = [ map [ map { int(rand(20)) + 1 } 1 .. 10 ], 1 .. 10];
Outer: foreach (@$a) {
foreach (@$_) {
print " $_";
if ($_ == 20) {
last Outer;
}
}
print "\n";
} print "\n";</lang>
PHP
<lang php><?php for ($i = 0; $i < 10; $i++)
for ($j = 0; $j < 10; $j++)
$a[$i][$j] = rand(1, 20);
foreach ($a as $row) {
foreach ($row as $element) {
echo " $element";
if ($element == 20)
break 2; // 2 is the number of loops we want to break out of
}
echo "\n";
} echo "\n"; ?></lang>
Python
Python has only inner loop breaks. Below are two solutions around this problem, the first uses exception handling:
<lang python> import random class Found20(Exception):
pass
number_array = [[random.randrange(1,21) for x in xrange(10)] for y in xrange(10)]
try:
for row in number_array:
for element in row:
print element,
if element == 20:
raise Found20
print
except Found20:
</lang>
The second uses a flag variable:
<lang python> import random
number_array = [[random.randrange(1,21) for x in xrange(10)] for y in xrange(10)] found20 = False
for row in number_array:
for element in row:
print element,
if element == 20:
found20 = True
break
print
if found20:
break
</lang>
The , after print element suppresses printing a line break. The above has been programmed on Python 2.6; I assume it also works on other Python 2.x versions, but it needs some minor changes in Python 3.
But the normal way to solve this problem in Python is to use a return inside a function: <lang python>from random import randint
def do_scan(m):
for row in m:
for item in row:
print item,
if item == 20:
print
return
print
m = [[randint(1, 20) for x in xrange(10)] for y in xrange(10)] do_scan(m)</lang>
R
<lang R> m <- 10 n <- 10 mat <- matrix(sample(1:20L, m*n, replace=TRUE), nrow=m); mat done <- FALSE for(i in seq_len(m)) {
for(j in seq_len(n))
{
cat(mat[i,j])
if(mat[i,j] == 20)
{
done <- TRUE
break
}
cat(", ")
}
if(done)
{
cat("\n")
break
}
} </lang>
Ruby
As the break command only jumps out of the innermost loop, this task requires Ruby's catch/throw functionality.
<lang ruby>srand
ary = (1..20).to_a.shuffle.each_slice(4).to_a
p ary
catch :found_it do
for row in ary
for element in row
print "%2d " % element
throw :found_it if element == 20
end
puts ","
end
end
puts "done"</lang>
[[2, 12, 10, 4], [18, 11, 9, 3], [14, 15, 7, 17], [6, 19, 8, 13], [1, 20, 16, 5]] 2 12 10 4 , 18 11 9 3 , 14 15 7 17 , 6 19 8 13 , 1 20 done
Tcl
Tcl only supports single-level breaks; exiting more deeply nested looping requires the use of exceptions, which are considerably more verbose before Tcl 8.6.
<lang tcl>set ary [subst [lrepeat 10 [lrepeat 5 {[expr int(rand()*20+1)]}]]]
try {
foreach row $ary {
foreach col $row {
puts -nonewline [format %3s $col]
if {$col == 20} {
throw MULTIBREAK "we're done"
}
}
puts ,
}
} trap MULTIBREAK {} {} puts " done"</lang> Sample output:
12 13 14 13 15, 1 14 7 16 3, 12 11 5 1 9, 12 5 1 4 2, 6 11 11 4 11, 7 14 20 done
TI-89 BASIC
The Stop statement exits the containing program.
Prgm
Local mat,i,j
© randMat(5, 5) exists but returns -9 to 9 rather than 1 to 20
newMat(5, 5) → mat
For i,1,rowDim(mat)
For j,1,colDim(mat)
rand(20) → mat[i,j]
EndFor
EndFor
Disp mat
Pause "Press a key."
ClrIO
For i,1,rowDim(mat)
For j,1,colDim(mat)
If mat[i,j] = 20 Then
Stop
Else
Output i*8, j*18, mat[i,j]
EndIf
EndFor
EndFor
EndPrgm