<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:
    def generateParenthesis(self, n: int) -> List[str]:
        tack = []

        res = []

        def backtrack(openN, closedN):
            if openN == closedN == n:
                res.append("".join(tack))

            if openN < n:
                tack.append("(")
                backtrack(openN + 1, closedN)
                tack.pop()
            
            if openN > closedN:
                tack.append(")")
                backtrack(openN, closedN + 1)
                tack.pop()

        backtrack(0, 0)
        return res
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