<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:
    vector<string> generateParenthesis(int n) {
        int c_open = n; int c_close = n;
        vector<string>res;
        string op = "";
        gen(c_open,c_close,res,op);
        return res;
    }
    void gen(int open,int close,vector<string>&res,string op){
        if(open == 0 && close == 0)
        {
            res.push_back(op);
            return;
        }
        if(open >= 0)
        {
            string op1 = op;
            op1 += '(';
            gen(open-1,close,res,op1); 
        }
        if(close > open){
            string op1 = op;
            op1 += ')';
            gen(open,close-1,res,op1);
        }          

    }
};
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