LeetCode47. Permutations II

一、题目

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

Example 1:

Input: nums = [1,1,2]
Output:
[[1,1,2],
[1,2,1],
[2,1,1]]
Example 2:

Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Constraints:

1 <= nums.length <= 8
-10 <= nums[i] <= 10

二、题解

class Solution {
public:
    vector<int> path;
    vector<vector<int>> res;
    void backtracking(vector<int>& nums,vector<int>& used){
        if(path.size() == nums.size()){
            res.push_back(path);
            return;
        }
        for(int i = 0;i < nums.size();i++){
            if(i > 0 && nums[i] == nums[i-1] && used[i-1] == 0) continue;
            if(used[i] == 1) continue;
            path.push_back(nums[i]);
            used[i] = 1;
            backtracking(nums,used);
            path.pop_back();
            used[i] = 0;
        }
    }
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        vector<int> used(nums.size(),0);
        backtracking(nums,used);
        return res;
    }
};