leetcode 46. 全排列----回溯篇5

class Solution {
	vector<vector<int>> ret;
	vector<int> num;
	vector<bool> visited;
public:
	vector<vector<int>> permute(vector<int>& nums) 
	{
		if (nums.empty()) return ret;
		visited.resize(nums.size(), false);
		backTrace(nums);
		return ret;
	}
	void backTrace(vector<int>& nums)
	{
		if (num.size() == nums.size())
		{
			ret.push_back(num);
			return;
		}
		for (int i =0; i < nums.size(); i++)
		{
			if (visited[i]) continue;
			num.push_back(nums[i]);
			visited[i] = true;
			backTrace(nums);
			num.pop_back();
			visited[i] = false;
		}
	}
};