PHP Program to print all permutations of a given string
Last Updated :
10 Dec, 2021
A permutation also called an “arrangement number” or “order,” is a rearrangement of the elements of an ordered list S into a one-to-one
A permutation also called an “arrangement number” or “order,” is a rearrangement of the elements of an ordered list S into a one-to-one correspondence with S itself. A string of length n has n! permutation.
Source: Mathword(http://mathworld.wolfram.com/Permutation.html)
Below are the permutations of string ABC.
ABC ACB BAC BCA CBA CAB
Here is a solution that is used as a basis in backtracking.
PHP
<?php
function permute( $str , $l , $r )
{
if ( $l == $r )
echo $str . "\n" ;
else
{
for ( $i = $l ; $i <= $r ; $i ++)
{
$str = swap( $str , $l , $i );
permute( $str , $l + 1, $r );
$str = swap( $str , $l , $i );
}
}
}
function swap( $a , $i , $j )
{
$temp ;
$charArray = str_split ( $a );
$temp = $charArray [ $i ] ;
$charArray [ $i ] = $charArray [ $j ];
$charArray [ $j ] = $temp ;
return implode( $charArray );
}
$str = "ABC" ;
$n = strlen ( $str );
permute( $str , 0, $n - 1);
?>
|
Output:
ABC
ACB
BAC
BCA
CBA
CAB
Algorithm Paradigm: Backtracking
Time Complexity: O(n*n!) Note that there are n! permutations and it requires O(n) time to print a permutation.
Auxiliary Space: O(r – l)
Note: The above solution prints duplicate permutations if there are repeating characters in the input string. Please see the below link for a solution that prints only distinct permutations even if there are duplicates in input.
Print all distinct permutations of a given string with duplicates.
Permutations of a given string using STL
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