LeetCode - Permutations

解法一：recursion

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> out;
        vector<int> visited(nums.size(), 0);
        gen(nums, 0, visited, out, res);
        return res;
    }
    void gen(vector<int>& nums, int pos, vector<int>& visited, vector<int>& out, vector<vector<int>>& res){
        if(pos == nums.size()) {
            res.push_back(out);
        }
        else{
            for(int i=0;i<nums.size();i++){
                if(visited[i]==0){
                    visited[i] = 1;
                    out.push_back(nums[i]);
                    gen(nums, pos+1, visited, out, res);
                    out.pop_back();
                    visited[i] = 0;
                }
            }
        }
    }
};