<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(set<string> &st,string s,int count,int n)
    {
        if(s.length()>=n)
        {
            if(count==0)
            st.insert(s);
            return ;
        } 
        if(count<0)
        return;
        if(count > 0) 
        {
            s += ')';
            solve(st, s, count - 1, n);
            s.pop_back(); 
        }
            s += '(';
            solve(st, s, count + 1, n);
            s.pop_back(); 
        

    }
    vector<string> generateParenthesis(int n) 
    {
     set<string>st;
     string s="(";
     solve(st,s,1,2*n);
     vector<string>ans;
     for(auto i:st)
     {
       ans.push_back(i);
     }
     return ans;   
    }
};
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