90. Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: [1,2,2]
Output:
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

 C++:

无重复子集问题：Subsets

class Solution {
public:
    void dfs(const vector<int> &S, vector<int>::iterator start, vector<int> &path, vector<vector<int> > &result) {
        result.push_back(path);
        for (auto i = start; i < S.end(); i++) {            //以每一个元素开头做一次深搜
            //if (i != start && *i == *(i - 1)) continue;   //同样起到跳过重复元素作用
            path.push_back(*i);
            dfs(S, i + 1, path, result);
            path.pop_back();
            while (i!=S.end()-1 && *i == *(i + 1)) //回溯时跳过重复的元素
                i++;
        }
    }

    vector<vector<int> > subsetsWithDup(vector<int> &S) {
        sort(S.begin(), S.end());
        vector<vector<int> > result;
        vector<int> path;
        dfs(S, S.begin(), path, result);
        return result;
    }
};