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
     
      
       > permute(vector
       
        & nums) {        vector
        
         
          > results;        sort(nums.begin(),nums.end());        vector
          
            temp; backtrace(nums, results, temp); return results; } void backtrace(vector
           
            & nums, vector
            
             
              >& results, vector
              
               & 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(); } }