Generate Parentheses
<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>
String; Dynamic Programming; Backtracking
/**
 * @param {number} n
 * @return {string[]}
 */
var generateParenthesis = function (n) {
    function dfs(l, r, t) {
        if (l > n || r > n || l < r) {
            return;
        }
        if (l == n && r == n) {
            ans.push(t);
            return;
        }
        dfs(l + 1, r, t + '(');
        dfs(l, r + 1, t + ')');
    }
    let ans = [];
    dfs(0, 0, '');
    return ans;
};
