LeetCode-46-Permutations

算法描述：

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]
]

解题思路：题目要求解除所有排列，首先想到的是回溯法。这个题目的关键点是去重。

    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> results;
        sort(nums.begin(),nums.end());
        vector<int> temp;
        backtrace(nums, results, temp);
        return results;
    }
    
    void backtrace(vector<int>& nums, vector<vector<int>>& results, vector<int>& temp){
        if(temp.size()==nums.size()){
            results.push_back(temp);
            return;
        }
        
        for(int i=0; i < nums.size(); i++){
            if(find(temp.begin(),temp.end(),nums[i]) !=temp.end()) continue;
            temp.push_back(nums[i]);
            backtrace(nums,results,temp);
            temp.pop_back();
        }
    }