[leetCode刷题笔记]46. Permutations

还是用backtrack呀

public class Solution {    public List<List<Integer>> permute(int[] nums) {        List<List<Integer>> res = new ArrayList<List<Integer>>();        helper(res, new ArrayList<Integer>(), nums);        return res;    }    private void helper(List<List<Integer>> res, List<Integer> per, int[] nums) {        if (per.size() == nums.length) {            res.add(new ArrayList<Integer>(per));            return;        }                for (int i = 0; i < nums.length; i++) {            if (per.contains(nums[i])) continue;            per.add(nums[i]);            helper(res, per, nums);            per.remove(per.size() - 1);        }    }}