# 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],
  []
]

# Solution

Approach 1: Recursion.

# Code (Python)

Approach 1:

# Code (C++)

Approach 1:

class Solution {
private:
    vector<vector<int>> subsets;
    void doSubsetsWithDup(vector<int>& nums, int head, int level, vector<int>& buf) {
        if (level == 0)
        {
            subsets.push_back(buf);
            return;
        }
        for (int i = head; i <= nums.size() - level; ++i)
        {
            if (i > head && nums[i] == nums[i-1])
                continue;
            buf.push_back(nums[i]);
            doSubsetsWithDup(nums, i + 1, level - 1, buf);
            buf.pop_back();
        }
    }
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        std::sort(nums.begin(), nums.end());
        vector<int> buf;
        for (int i = 0; i <= nums.size(); ++i)
        {
            doSubsetsWithDup(nums, 0, i, buf);
        }
        return subsets;
    }
};