46. 全排列 Permutations

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

 

方法 ：

回溯法。 

 

public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> res = new ArrayList<List<Integer>>();

        List<Integer> output = new ArrayList<Integer>();
        for (int num : nums) {
            output.add(num);
        }

        int n = nums.length;
        backtrack(n, output, res, 0);
        return res;
    }

    public void backtrack(int n, List<Integer> output, List<List<Integer>> res, int first) {
        if (first == n) {
            res.add(new ArrayList<Integer>(output));
        }
        for (int i = first; i < n; i++) {
            Collections.swap(output, first, i);
            backtrack(n, output, res, first + 1);
            Collections.swap(output, first, i);
        }
    }

 

参考链接：

https://leetcode.com/problems/permutations/

https://leetcode-cn.com/problems/permutations/