问题描述：

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1],[3,1,2], and [3,2,1].

基本思想：

利用了C++STL的组合数的性质

代码：

#include <algorithm>   //C++
class Solution {
public:
    vector<vector<int> > permute(vector<int> &num) {
        int size = num.size();
        sort(num.begin(),num.end());
        
        vector<vector<int> > result;
        vector<int> first;
        for(int i = 0; i <size ; i++){
            first.push_back(num[i]);
        }
        result.push_back(first);
        
        while(next_permutation(num.begin(),num.end())){
            vector<int> tmp;
            for(int i = 0; i <size ; i++){
                tmp.push_back(num[i]);
            }
            result.push_back(tmp);
            
        }
        return result;
    }
};

[leetcode]