19.2.7 [LeetCode 47] Permutations II

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

Example:

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

class Solution {
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        set<vector<int>>ans;
        ans.insert(vector<int>(1, nums[0]));
        for (int i = 1; i < nums.size(); i++) {
            set<vector<int>>tmp = ans;
            ans.clear();
            for (auto j = tmp.begin(); j != tmp.end(); j++) {
                vector<int>now = *j;
                for (int k = 0; k <= now.size(); k++) {
                    now.insert(now.begin() + k, nums[i]);
                    ans.insert(now);
                    now.erase(now.begin() + k);
                }
            }
        }
        return vector<vector<int>>(ans.begin(),ans.end());
    }
};

单纯只是把上一道改了一下