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：

<?phpfunction 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"
}

希望本文所述对大家PHP程序设计有所帮助。