[LeetCode] Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,2], a solution is:

[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

class Solution {
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        vector<vector<int>> res(1);
        sort(nums.begin(), nums.end());
        int lastSize;
        for(int i=0;i<nums.size();i++)
        {
            int start = 0;
            int size = res.size();
            if(i>0 && nums[i] == nums[i-1])
            {
                start = size - lastSize;
            }
            for(int j=start;j<size;j++)
            {
                vector<int> tmp = res[j];
                tmp.push_back(nums[i]);
                res.push_back(tmp);
            }
            lastSize = size - start;
        }
        return res;
    }
};