JAVA版《集合的所有子集》

回溯算法

import java.util.*;
public class Solution {
    ArrayList<ArrayList<Integer>> res = new ArrayList<>();
    public ArrayList<ArrayList<Integer>> subsets(int[] S) {
        LinkedList<Integer> track = new LinkedList<>();
        back(S, 0, track);
        return res;
    }
    public void back(int[] S, int start, LinkedList<Integer> track){
        res.add(new ArrayList<>(track));
        for(int i = start; i < S.length; i++){
            track.add(S[i]);
            back(S, i+1, track);
            //撤销 回溯
            track.removeLast();
        }
    }
}