Solution.php

class Solution {

    /**
     * @param integer[] $nums
     * @return void
     */

    function nextPermutation(&$nums) {
        $n = count($nums);
        $i = $n - 2;
        while ($i >= 0 && $nums[$i] >= $nums[$i + 1]) {
            $i--;
        }
        if ($i >= 0) {
            $j = $n - 1;
            while ($j >= $i && $nums[$j] <= $nums[$i]) {
                $j--;
            }
            $temp = $nums[$i];
            $nums[$i] = $nums[$j];
            $nums[$j] = $temp;
        }
        $this->reverse($nums, $i + 1, $n - 1);
    }

    function reverse(&$nums, $start, $end) {
        while ($start < $end) {
            $temp = $nums[$start];
            $nums[$start] = $nums[$end];
            $nums[$end] = $temp;
            $start++;
            $end--;
        }
    }
}