[leetcode-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:
[
"((()))",
"(()())",
"(())()",
"()(())",
"()()()"
]

思路：

DFS.

void addParenthesis(vector<string>& res, string str, int open, int close,int n)
     {
         if (str.length() == n*2)
         {
             res.push_back(str);
             return;
         }
         if (open<n)addParenthesis(res, str + "(", open + 1, close, n);
         if (close < open)addParenthesis(res, str + ")", open, close + 1, n);         
     }
     vector<string> generateParenthesis(int n)
     {
         vector<string>res;
         addParenthesis(res, "", 0, 0, n);
         return res;
     }

参考：

https://discuss.leetcode.com/topic/4485/concise-recursive-c-solution