47. Permutations II

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

For example,
[1,1,2] have the following unique permutations:

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

递归的思路很清晰，速度慢了很多

class Solution {public:    set<vector<int>> res;    void Func(vector<int>& nums1, int idx){        if(idx == nums1.size())            res.insert(nums1);        else {            for(int i = idx; i < nums1.size(); ++i){                swap(nums1[i], nums1[idx]);                Func(nums1, idx + 1);                swap(nums1[i], nums1[idx]);            }        }    }    vector<vector<int>> permuteUnique(vector<int>& nums) {        if(nums.size() == 0)            return vector<vector<int>>();        Func(nums, 0);        return vector<vector<int>>(res.begin(), res.end());        }};