[leetcode] 46. Permutations

题目：

Given a collection of distinct integers, return all possible permutations.

Example:

Input: [1,2,3]
Output:
[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

代码：

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int> > res;
        deal(res, vector<int>(), nums);
        return res;
    }
    
    void deal(vector<vector<int> >& res, vector<int> temp, vector<int> nums){
        if(temp.size() == nums.size()){
            res.push_back(temp);
        }
        for(int i = 0; i < nums.size(); i++){
            bool flag = true;
            for(int j = 0; j < temp.size(); j++){
                if(temp[j] == nums[i]){
                    flag = false;
                }
            }
            if(flag){
                temp.push_back(nums[i]);
                deal(res, temp, nums);
                temp.pop_back();
            }
        }
    }
};