<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 generateP(int op, int cl, int n, string s, vector<string>&res){
        if(op == n && cl==n){
            res.push_back(s);
            return;
        }
        if(op <= n )generateP(op+1,cl,n,s+"(",res);
        if(op > cl)
        generateP(op, cl+1, n, s+")", res);
    }
    vector<string> generateParenthesis(int n) {
        vector<string>res;
        generateP(0,0,n,"",res);
        return res;
    }
};
19994