Leetcode Permutations

题意：生成排列数。

思路：DFS。

class Solution {public:    vector <vector<int> > re;    vector<vector<int>> permute(vector<int>& nums) {        dfs(nums, 0);        return re;    }        int dfs(vector<int> sub, int k) {        if(sub.size() - 1 == k) {            re.push_back(sub);            return 0;        }                vector<int> temp;        int ch;        for(int i = k; i < sub.size(); ++ i) {            temp = sub;            ch = temp[k];            temp[k] = temp[i];            temp[i] = ch;                        dfs(temp, k + 1);        }        return 0;    }};