题目链接

回溯

class Solution {
    List<List<Integer>> res = new ArrayList<List<Integer>>();
    List<Integer> list = new ArrayList<Integer>();
    boolean[] used; 
    public List<List<Integer>> subsetsWithDup(int[] nums) {
        used = new boolean[nums.length];
        Arrays.fill(used, false);
        Arrays.sort(nums);
        backtracking(nums, 0);
        return res;
    }
    public void backtracking(int[] nums, int startIndex){
    	// 求全部子集
        res.add(new ArrayList<>(list));
        for(int i = startIndex; i < nums.length; i++){
        	// 去重
            if(i > 0 && nums[i] == nums[i - 1] && used[i - 1] == false){
                continue;
            }
            used[i] = true;
            list.add(nums[i]);
            backtracking(nums, i + 1);
            used[i] = false;
            list.removeLast();
        }
    }
}

本题是子集问题+组合求和Ⅲ的综合