<"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');
"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"

}


更多关于PHP相关内容感兴趣的读者可查看本站专题：《PHP数据结构与算法教程》、《php程序设计算法总结》、《php字符串(string)用法总结》、《PHP数组(Array)操作技巧大全》、《PHP常用遍历算法与技巧总结》及《PHP数学运算技巧总结》
希望本文所述对大家PHP程序设计有所帮助。