回溯 02

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

代码如下

class Solution {
    public List<List<Integer>> subsets(int[] nums) {
        List<List<Integer>> res = new ArrayList<>();
        backtrack(0, nums, res, new ArrayList<Integer>());
        return res;
    }

    public void backtrack(int index, int[] nums, List<List<Integer>> res, ArrayList<Integer> temp) {
        res.add(new ArrayList<>(temp)); // 每一次递归下一个值，都存入子集中
        for (int j = index; j < nums.length; j++) {
            temp.add(nums[j]);
            backtrack(j + 1, nums, res, temp);
            temp.remove(temp.size() - 1);   // 回溯回原来的状态
        }
    }
}