PHP 排列组合

悠悠 2021-09-15 10:44 377阅读 0赞

几个排列组合例子：【递归】

一、出处：[对数组作排列组合的PHP算法 | maraboy][PHP_ _ maraboy]

function array_comb($array, $n) { 
        $results = [];
        // case $n == 1, give straightforward result
        if ($n == 1) { 
            foreach ($array as $key => $value)
                $results[] = array($key => $value);
            return $results;
        }
        // case $n > 1
        // sort the array by key to make key comparison possible later
        ksort($array);
        // get combination results for n - 1 array, where m is count of array elements
        $subarray = array_slice($array, 1, null, true);
        $subarray_results = array_comb($subarray, $n - 1);
        // cross merge the m array elements with n - 1 array results
        foreach ($array as $key => $value)
            foreach ($subarray_results as $subarray_result)
                if ($key < array_shift(array_keys($subarray_result)))
                    $results[] = array($key => $value) + $subarray_result;
        return $results;
    }

执行结果如下：

# 假设执行 array_comb(['[1:1]', '[2:2]', '[3:3]'], 2); 并 var_dump 出来
    array (size=3)
      0 => 
        array (size=2)
          0 => string '[1:1]' (length=5)
          1 => string '[2:2]' (length=5)
      1 => 
        array (size=2)
          0 => string '[1:1]' (length=5)
          2 => string '[3:3]' (length=5)
      2 => 
        array (size=2)
          1 => string '[2:2]' (length=5)
          2 => string '[3:3]' (length=5)
    
    # 将 return 前一行修改一下，即
    $results[] = array($key => $value) + $subarray_result;
    # 修改为
    $results[] = $value . ',' . $subarray_result[key($subarray_result)];
    #-------------------------------------------------------------------#
    # 得到另一种结果：
    array (size=3)
      0 => string '[1:1],[2:2]' (length=11)
      1 => string '[1:1],[3:3]' (length=11)
      2 => string '[2:2],[3:3]' (length=11)

--------------------

二、

执行结果如下：

0 => 
      array (size=2)
        0 => string '[1:1]' (length=5)
        1 => string '[2:2]' (length=5)
    1 => 
      array (size=2)
        0 => string '[1:1]' (length=5)
        1 => string '[3:3]' (length=5)
    2 => 
      array (size=2)
        0 => string '[2:2]' (length=5)
        1 => string '[3:3]' (length=5)

--------------------

三、

执行结果如下：

# 直接就是组合字符串
    array (size=3)
      0 => string '[1:1],[2:2]' (length=11)
      1 => string '[1:1],[3:3]' (length=11)
      2 => string '[2:2],[3:3]' (length=11)

--------------------

[PHP_ _ maraboy]: http://maraboy.com/node/88