<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 recur(string curr, vector<string> &ans, int l, int openCount, int closedCount, int n) {
        if(l==2*n && openCount == closedCount) {
            ans.push_back(curr);
            return;
        }
        if(openCount<=n)
            recur(curr+"(", ans, l+1, openCount+1, closedCount, n);
        
        if(closedCount<openCount)
            recur(curr+")", ans, l+1, openCount, closedCount+1, n);
        return;
    }
    vector<string> generateParenthesis(int n) {
        vector<string> ans;
        if(n==0)
            return {};
        recur("", ans, 0, 0, 0, n);
        return ans;
    }
};
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