<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 solve(int cnt,int n,string s){
        if(cnt>n ||cnt<0 || s.length()>n*2) return;

        if(cnt==0 && s.length()==n*2){
            ans.push_back(s);
            return;
        }

        solve(cnt+1,n,s+"(");
        solve(cnt-1,n,s+")");
    }
    vector<string> generateParenthesis(int n) {
        int cnt=0;
        string s="";
        solve(cnt,n,s);
        return ans;
    }
};
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