22. Generate Parentheses

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

For example, given n = 3, a solution set is:

"((()))", "(()())", "(())()", "()(())", "()()()"

解题思路：

DFS

class Solution { public: vector<string> generateParenthesis(int n) { vector<string>res; if(n==0)return res; dfs(res,n,0,0,""); return res; } void dfs(vector<string>&res,int n,int l,int r,string s){ if(l==n&&r==n){ res.push_back(s); return ; } if(l==n){ dfs(res,n,l,r+1,s+")"); return ; } if(l==r){ dfs(res,n,l+1,r,s+"("); return ; } dfs(res,n,l+1,r,s+"("); dfs(res,n,l,r+1,s+")"); } };