<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> ans;
void func(int n,string s,int op,int cl){
    if(s.length() == 2*n){
        ans.push_back(s);
        return;
    }
        if(op < n){
        s = s + "(";
        func(n,s,op+1,cl);
        s.pop_back();
        }
        if(cl < op){
        s = s + ")";
        func(n,s,op,cl+1);
        s.pop_back();
        } 
}
    vector<string> generateParenthesis(int n) {
        func(n,"",0,0);
        return ans;
    }
};
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