<p>Given <code>n</code> pairs of parentheses, write a function to <em>generate all combinations of well-formed parentheses</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> n = 3
<strong>Output:</strong> ["((()))","(()())","(())()","()(())","()()()"]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> n = 1
<strong>Output:</strong> ["()"]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 8</code></li>
</ul>

class Solution {
public:
    void solve(string op, int open, int close, vector<string> &ans){
        if(open == 0 && close == 0){
            ans.push_back(op);
            return;
        }
        if(open == 0 && close > 0){
            ans.push_back(op + std::string(close, ')'));
            return;
        }
        if(close == 0){
            return;
        }
        //when count of open and close brackets are same then 
        //we have only one choice to put open bracket 
        if(open == close){
            solve(op + '(', open-1, close, ans);
        } else{
            solve(op + '(', open-1, close, ans);
            solve(op + ')', open, close-1, ans);
        }
    }
    vector<string> generateParenthesis(int n) {
        int open = n;
        int close = n;
        vector<string> ans;
        string op = "";
        solve(op, open, close, ans);
        return ans;
    }
};
13615