LeetCode (Subsets II)

Problem:

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

Note: 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],
[]
]

Solution:
class Solution {
public:
vector<vector<int>> subsetsWithDup(vector<int>& nums) {
if(nums.empty()) return {{}};
sort(nums.begin(), nums.end());
vector<vector<int>> ans;
int n = nums.back();
nums.pop_back();
vector<vector<int>> pre = subsetsWithDup(nums);
for(int i = 0; i < pre.size(); i++){
ans.push_back(pre[i]);
vector<int> temp = pre[i];
temp.push_back(n);
if(find(pre.begin(), pre.end(), temp) == pre.end())
ans.push_back(temp);
}
return ans;
}
};