Cannot access the function return variable

Question

cannot return function value, if i print inside the function the value had printed when i make return variable that that it will be return zero my code following

    function permute($str,$i,$n) {
$b="";
   if ($i == $n)
        $b .=$str.",";
   else {
        for ($j = $i; $j < $n; $j++) {
          swap($str,$i,$j);
          permute($str, $i+1, $n);
          swap($str,$i,$j); // backtrack.
       }

   }

   return $b;


}
function swap(&$str,$i,$j) {
    $temp = $str[$i];
    $str[$i] = $str[$j];
    $str[$j] = $temp;
}   
$str = "375";
$test=permute($str,0,strlen($str));
echo $test;

@Nouphal.M, Put that as an answer mate.

Shankar Narayana Damodaran
– Shankar Narayana Damodaran

2014-02-21 06:57:29 +00:00
Commented Feb 21, 2014 at 6:57 — Shankar Narayana Damodaran
– Shankar Narayana Damodaran, Commented Feb 21, 2014 at 6:57
yes i need array with possible permutations

Stephen Raj
– Stephen Raj

2014-02-21 07:02:49 +00:00
Commented Feb 21, 2014 at 7:02 — Stephen Raj
– Stephen Raj, Commented Feb 21, 2014 at 7:02
Nouphal.M : thanks dude i got it

Stephen Raj
– Stephen Raj

2014-02-21 07:04:49 +00:00
Commented Feb 21, 2014 at 7:04 — Stephen Raj
– Stephen Raj, Commented Feb 21, 2014 at 7:04
Sorry @Sankar i went for friday namaz

Nouphal.M
– Nouphal.M

2014-02-21 09:41:10 +00:00
Commented Feb 21, 2014 at 9:41 — Nouphal.M
– Nouphal.M, Commented Feb 21, 2014 at 9:41

Jiří Chmiel · Accepted Answer · 2014-02-21 06:58:01Z

2

  function permute($str,$i,$n) {
   ....
          $b . = permute($str, $i+1, $n);
   ....

   return $b;


}

You are not using the result of inner call.

answered Feb 21, 2014 at 6:58

Jiří Chmiel

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2 Comments

Abhishek kadadi Over a year ago

ya sorry. he is not returning any thing from swap

Stephen Raj Over a year ago

its ok ya i got that]

Akhil Sidharth · Accepted Answer · 2014-02-21 07:19:42Z

0

You have to use the return value in the loop

<?php
function permute($str,$i,$n){
    $b=NULL;
    if ($i == $n){
        $b= $str.",";
     }else {
        for ($j = $i; $j < $n; $j++){
        swap($str,$i,$j);
        $b.=permute($str, $i+1, $n); //ERROR HERE
        swap($str,$i,$j); // backtrack.
        }
    }
    return $b;
}

edited Feb 21, 2014 at 7:19

answered Feb 21, 2014 at 6:55

Akhil Sidharth

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Comments

Ja͢ck · Accepted Answer · 2014-02-21 07:16:45Z

0

This doesn't tell you exactly why your function was wrong, but this is how you would generate an array of possible permutations:

// permute prefix $s with set $r and store results in $a
function permute($r, array &$a, $s = '')
{
    if (!strlen($r)) {
        $a[] = $s; // store result
        return;
    }

    for ($i = 0; $i < strlen($r); ++$i) {
        // recurse
        permute(substr_replace($tmp = $r, '', $i, 1), $a, $s . $r[$i]);
    }
}

$str = "375"; 
$res = [];

permute($str, $res);

print_r($res);

answered Feb 21, 2014 at 7:16

community wiki

Ja͢ck

1 Comment

Stephen Raj Over a year ago

Thanks dude but i got the result

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