n选m 的所有组合无递归的算法 php实现

最新推荐文章于 2021-07-30 17:31:16 发布

原创最新推荐文章于 2021-07-30 17:31:16 发布 · 1k 阅读

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本文介绍了如何使用PHP实现n选m的所有组合，不依赖递归方式。通过特定算法原理，可以高效地计算出组合结果。

n选m的组合的 php实现

原理：http://xiaomage.blog.51cto.com/293990/74094/

function cs($n, $m) {
    if ($n == $m) {
        return array(array_fill(0, $m, 1));
    }
    $rs = array();
    $arr = array_merge(array_fill(0, $m, 1), array_fill(0, $n - $m, 0));
    $rs[] = $arr;
    while (true) {
        $str = implode('', $arr);
        $pos = strpos($str, '10');
        if ($pos === false) {
            break;
        } else {
            if ($pos > 1) {
                $tmp = array_slice($arr, 0, $pos);
                rsort($tmp);
                array_splice($arr, 0, $pos, $tmp);
            }
            $arr[$pos] = 0;
            $arr[$pos + 1] = 1;
            $rs[] = $arr;
        }
    }
    return $rs;
}

$rs = cs(5, 3);
print_r($rs);

结果

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 1
            [2] => 1
            [3] => 0
            [4] => 0
        )

    [1] => Array
        (
            [0] => 1
            [1] => 1
            [2] => 0
            [3] => 1
            [4] => 0
        )

    [2] => Array
        (
            [0] => 1
            [1] => 0
            [2] => 1
            [3] => 1
            [4] => 0
        )

    [3] => Array
        (
            [0] => 0
            [1] => 1
            [2] => 1
            [3] => 1
            [4] => 0
        )

    [4] => Array
        (
            [0] => 1
            [1] => 1
            [2] => 0
            [3] => 0
            [4] => 1
        )

    [5] => Array
        (
            [0] => 1
            [1] => 0
            [2] => 1
            [3] => 0
            [4] => 1
        )

    [6] => Array
        (
            [0] => 0
            [1] => 1
            [2] => 1
            [3] => 0
            [4] => 1
        )

    [7] => Array
        (
            [0] => 1
            [1] => 0
            [2] => 0
            [3] => 1
            [4] => 1
        )

    [8] => Array
        (
            [0] => 0
            [1] => 1
            [2] => 0
            [3] => 1
            [4] => 1
        )

    [9] => Array
        (
            [0] => 0
            [1] => 0
            [2] => 1
            [3] => 1
            [4] => 1
        )

)