leetcode 刷题之路 12 Permutations

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].

全排列问题，详细分析参考这篇文章，这里不再赘述，直接贴出代码。

class Solution {public:vector<vector<int> > permute(vector<int> &num){vector<vector<int>> result;helper(num, result, 0, num.size());return result;}static void helper(vector<int> &num,vector<vector<int>> &result, int current, int len){if (current == len){result.push_back(num);return;}for (int i = current; i < len; i++){swap(num[current], num[i]);helper(num, result, current + 1, len);swap(num[current], num[i]);}}static void swap(int &a, int &b){int temp = a;a = b;b = temp;}};