php实现的生成排列算法示例

本文实例讲述了php实现的生成排列算法。分享给大家供大家参考，具体如下：<?phpfuncti

本文实例讲述了php实现的生成排列算法。分享给大家供大家参考，具体如下：

<?php
function perm($s, $n, $index)
{
 if($n == 0)
 {
 return '';
 }
 else
 {
 $nIndex = count($index); //可用的字符串下标
 $res = array();
 foreach($index as $i => $v)
 {
 $tmp = $index;
 unset($tmp[$i]); //去掉当前的前缀
 /* 调试信息，便于理解
 echo "len $n , cur $i , index:\n";
 var_dump($tmp);
 */
 $ret = perm($s, $n-1, $tmp); //递归得到稍短的排列
 if($ret != '')
 {
 foreach($ret as $r)
 {
 $res[] = $s[$v] . $r; //将稍短的排列逐个拼上当前的前缀
 }
 }
 else
 {
 $res[] = $s[$v];
 }
 }
 return $res;
 }
}
function getPerm($s)
{
 $n = strlen($s);
 $index = range(0, $n-1);
 //得到不同长度的排列
 for($i=1; $i<=$n; $i++)
 {
 var_dump(perm($s, $i, $index));
 }
}
getPerm('abcd');
?>

运行结果：

array(4) {   [0]=>   string(1) "a"   [1]=>   string(1) "b"   [2]=>   string(1) "c"   [3]=>   string(1) "d" } array(12) {   [0]=>   string(2) "ab"   [1]=>   string(2) "ac"   [2]=>   string(2) "ad"   [3]=>   string(2) "ba"   [4]=>   string(2) "bc"   [5]=>   string(2) "bd"   [6]=>   string(2) "ca"   [7]=>   string(2) "cb"   [8]=>   string(2) "cd"   [9]=>   string(2) "da"   [10]=>   string(2) "db"   [11]=>   string(2) "dc" } array(24) {   [0]=>   string(3) "abc"   [1]=>   string(3) "abd"   [2]=>   string(3) "acb"   [3]=>   string(3) "acd"   [4]=>   string(3) "adb"   [5]=>   string(3) "adc"   [6]=>   string(3) "bac"   [7]=>   string(3) "bad"   [8]=>   string(3) "bca"   [9]=>   string(3) "bcd"   [10]=>   string(3) "bda"   [11]=>   string(3) "bdc"   [12]=>   string(3) "cab"   [13]=>   string(3) "cad"   [14]=>   string(3) "cba"   [15]=>   string(3) "cbd"   [16]=>   string(3) "cda"   [17]=>   string(3) "cdb"   [18]=>   string(3) "dab"   [19]=>   string(3) "dac"   [20]=>   string(3) "dba"   [21]=>   string(3) "dbc"   [22]=>   string(3) "dca"   [23]=>   string(3) "dcb" } array(24) {   [0]=>   string(4) "abcd"   [1]=>   string(4) "abdc"   [2]=>   string(4) "acbd"   [3]=>   string(4) "acdb"   [4]=>   string(4) "adbc"   [5]=>   string(4) "adcb"   [6]=>   string(4) "bacd"   [7]=>   string(4) "badc"   [8]=>   string(4) "bcad"   [9]=>   string(4) "bcda"   [10]=>   string(4) "bdac"   [11]=>   string(4) "bdca"   [12]=>   string(4) "cabd"   [13]=>   string(4) "cadb"   [14]=>   string(4) "cbad"   [15]=>   string(4) "cbda"   [16]=>   string(4) "cdab"   [17]=>   string(4) "cdba"   [18]=>   string(4) "dabc"   [19]=>   string(4) "dacb"   [20]=>   string(4) "dbac"   [21]=>   string(4) "dbca"   [22]=>   string(4) "dcab"   [23]=>   string(4) "dcba" }