leetcode46

题目：

给定一个没有重复数字的序列，返回其所有可能的全排列。

示例:

输入: [1,2,3]
输出:
[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

解题思路：

DFS，递归。

代码：

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