LeetCode-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],
  []
]

题解：

第一次使用visit数组记录访问情况超时。

更进思路后，先对nums排序，然后进行dfs，每个点作为起始点进行遍历，set暴力去重。

class Solution {
public:
  void dfs(vector<int>& nums, set<vector<int>>& res, vector<int>& idx, int n, int k) {
    sort(idx.begin(), idx.end());
    res.insert(idx);
    for (int i = k; i < n; i++) {
        idx.push_back(nums[i]);
        dfs(nums, res, idx, n, i + 1);
        idx.pop_back();
      }
  }
  vector<vector<int>> subsetsWithDup(vector<int>& nums) {
    int n = nums.size();
    set<vector<int>> res;
    vector<int> idx;
    sort(nums.begin(), nums.end());
    dfs(nums, res, idx, n, 0);
    vector<vector<int>> ans(res.begin(), res.end());
    return ans;
  }
};