leetcode 22. 括号生成

//dfs回溯

	class Solution {
	public:
		vectorans;
		void dfs(int l,int r,int n,string temp)
		{
			if(l==n&&r==n)
			{
			ans.push_back(temp);//收集解
			return ;
			}

			if(l generateParenthesis(int n) {
       	 if(n==0)return vector();
       	 string temp;
       	 dfs(0,0,n,temp);
 		return ans;
   	 }
	};