Leetcode_78_子集_dfs

我这个start就很妙，完美去重

// 冲刺063
import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;

// 冲刺063
class Solution {
    public List<List<Integer>> subsets(int[] nums) {
        List<List<Integer>> ans = new ArrayList<>();
        dfs(nums, new LinkedList<>(), ans, 0);
        return ans;
    }

    void dfs(int[] nums, Deque<Integer> now, List<List<Integer>> ans, int start) {
        ans.add(new ArrayList<>(now));
        for (int i = start; i < nums.length; i++) {
            now.push(nums[i]);
            dfs(nums, now, ans, i + 1);
            now.pop();
        }
    }
}