2021-4-8 回溯+dfs（数组全排列问题）

题目：leetcode 46

class Solution {
public:
    void dfs(vector<int> nums,vector<int> path,int dept,vector<bool> used){
        if(dept==nums.size()){
            res.push_back(path);
            return;
        }
        for(int i=0;i<nums.size();i++){
            if(used[i]){
                continue;
            }
            path.push_back(nums[i]);
            used[i]=1;
            dfs(nums,path,dept+1,used);   
            //回溯的意思是之前有的操作需要全部把它调整回来
            //状态重置
            path.pop_back();
            used[i]=0;
        }
    }
    vector<vector<int>> permute(vector<int>& nums) {
        int n=nums.size();
        int dept=0;
        vector<bool> used(n,false);
        vector<int> path;
        dfs(nums,path,dept,used);
        return res;
    }
private:
vector<vector<int>> res;
};