LeetCode-in-All

46. Permutations

Medium

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:

Input: nums = [1,2,3]

Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:

Input: nums = [0,1]

Output: [[0,1],[1,0]]

Example 3:

Input: nums = [1]

Output: [[1]]

Constraints:

• 1 <= nums.length <= 6
• -10 <= nums[i] <= 10
• All the integers of nums are unique.

Solution

class Solution {
    /**
     * @param Integer[] $nums
     * @return Integer[][]
     */
    public function permute($nums) {
        if ($nums == null || count($nums) == 0) {
            return array();
        }
        $finalResult = array();
        $this->permuteRecur($nums, $finalResult, array(), array_fill(0, count($nums), false));
        return $finalResult;
    }

    private function permuteRecur($nums, &$finalResult, $currResult, $used) {
        if (count($currResult) == count($nums)) {
            array_push($finalResult, $currResult);
            return;
        }
        for ($i = 0; $i < count($nums); $i++) {
            if ($used[$i]) {
                continue;
            }
            array_push($currResult, $nums[$i]);
            $used[$i] = true;
            $this->permuteRecur($nums, $finalResult, $currResult, $used);
            $used[$i] = false;
            array_pop($currResult);
        }
    }
}

This site is open source. Improve this page.