<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(int x,string& s,vector<string>&v,int cur){
        if(x==0){
            if(cur==0) v.push_back(s);
            return;
        }
        string s1=s+"(";
        string s2=s+")";
        if(cur>=0 && x-cur>=1)
            solve(x-1,s1,v,cur+1);
        if(cur>0)
            solve(x-1,s2,v,cur-1);
        return;

    }
    vector<string> generateParenthesis(int n) {
        vector<string> v;
        string s="";
        solve(2*n,s,v,0);
        return v;
    }
};
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