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"title": "Minimum Height Trees",
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"content": "<p>A tree is an undirected graph in which any two vertices are connected by <i>exactly</i> one path. In other words, any connected graph without simple cycles is a tree.</p>\n\n<p>Given a tree of <code>n</code> nodes labelled from <code>0</code> to <code>n - 1</code>, and an array of <code>n - 1</code> <code>edges</code> where <code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> indicates that there is an undirected edge between the two nodes <code>a<sub>i</sub></code> and <code>b<sub>i</sub></code> in the tree, you can choose any node of the tree as the root. When you select a node <code>x</code> as the root, the result tree has height <code>h</code>. Among all possible rooted trees, those with minimum height (i.e. <code>min(h)</code>) are called <strong>minimum height trees</strong> (MHTs).</p>\n\n<p>Return <em>a list of all <strong>MHTs'</strong> root labels</em>. You can return the answer in <strong>any order</strong>.</p>\n\n<p>The <strong>height</strong> of a rooted tree is the number of edges on the longest downward path between the root and a leaf.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/09/01/e1.jpg\" style=\"width: 800px; height: 213px;\" />\n<pre>\n<strong>Input:</strong> n = 4, edges = [[1,0],[1,2],[1,3]]\n<strong>Output:</strong> [1]\n<strong>Explanation:</strong> As shown, the height of the tree is 1 when the root is the node with label 1 which is the only MHT.\n</pre>\n\n<p><strong>Example 2:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/09/01/e2.jpg\" style=\"width: 800px; height: 321px;\" />\n<pre>\n<strong>Input:</strong> n = 6, edges = [[3,0],[3,1],[3,2],[3,4],[5,4]]\n<strong>Output:</strong> [3,4]\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= n <= 2 * 10<sup>4</sup></code></li>\n\t<li><code>edges.length == n - 1</code></li>\n\t<li><code>0 <= a<sub>i</sub>, b<sub>i</sub> < n</code></li>\n\t<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>\n\t<li>All the pairs <code>(a<sub>i</sub>, b<sub>i</sub>)</code> are distinct.</li>\n\t<li>The given input is <strong>guaranteed</strong> to be a tree and there will be <strong>no repeated</strong> edges.</li>\n</ul>\n",
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