LeetCode:Permutations

题目描述：

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].

代码：

class Solution
{
	public:
		void swap(int * a,int * b)
		{
			int temp = *a;
			*a = *b;
			*b = temp;
		}

		void permuteRecursive(vector<int> & num,int begin,vector<vector<int>> & result)
		{
			if(begin == num.size())
			{
				result.push_back(num);
				return;
			}

			for(int i = begin;i < num.size();i++)
			{
				swap(&num[begin],&num[i]);
				permuteRecursive(num,begin+1,result);
				swap(&num[begin],&num[i]);
			}
		}

		vector<vector<int>> permute(vector<int> & nums)
		{
			vector<vector<int>> result;
			permuteRecursive(nums,0,result);
			return result;
		}
};