leetcode 47. Permutations II 搜索

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) {
        vector<vector<int>> res;
        sort(nums.begin(), nums.end());
        dfs(res, nums, 0);
        return res;
    }
    void dfs(vector<vector<int>>& res, vector<int> a, int begin){
        if(begin==a.size()-1){
            res.push_back(a);
            return;
        }
        for(int i=begin;i<a.size();i++){
            if(i!=begin&&a[i]==a[begin])continue;
            swap(a[i],a[begin]);
            dfs(res,a,begin+1);
        }
    }
};