Add solution #310

Author: JoshCrozier

0310-minimum-height-trees.js

@@ -0,0 +1,54 @@
+/**
+ * 310. Minimum Height Trees
+ * https://leetcode.com/problems/minimum-height-trees/
+ * Difficulty: Medium
+ *
+ * A tree is an undirected graph in which any two vertices are connected by exactly one
+ * path. In other words, any connected graph without simple cycles is a tree.
+ *
+ * Given a tree of n nodes labelled from 0 to n - 1, and an array of n - 1 edges where
+ * edges[i] = [ai, bi] indicates that there is an undirected edge between the two nodes
+ * ai and bi in the tree, you can choose any node of the tree as the root. When you select
+ * a node x as the root, the result tree has height h. Among all possible rooted trees,
+ * those with minimum height (i.e. min(h))  are called minimum height trees (MHTs).
+ *
+ * Return a list of all MHTs' root labels. You can return the answer in any order.
+ *
+ * The height of a rooted tree is the number of edges on the longest downward path
+ * between the root and a leaf.
+ */
+
+/**
+ * @param {number} n
+ * @param {number[][]} edges
+ * @return {number[]}
+ */
+var findMinHeightTrees = function(n, edges) {
+  if (n === 1) return [0];
+
+  const lookup = new Array(n).fill().map(() => new Set());
+  for (const [a, b] of edges) {
+    lookup[a].add(b);
+    lookup[b].add(a);
+  }
+
+  let result = [];
+  for (let i = 0; i < n; i++) {
+    if (lookup[i].size === 1) result.push(i);
+  }
+
+  while (n > 2) {
+    n -= result.length;
+    const modified = [];
+    for (const item of result) {
+      const adj = lookup[item].values().next().value;
+      lookup[adj].delete(item);
+      if (lookup[adj].size === 1) {
+        modified.push(adj);
+      }
+    }
+    result = modified;
+  }
+
+  return result;
+};

README.md

@@ -252,6 +252,7 @@
 306|[Additive Number](./0306-additive-number.js)|Medium|
 307|[Range Sum Query - Mutable](./0307-range-sum-query-mutable.js)|Medium|
 309|[Best Time to Buy and Sell Stock with Cooldown](./0309-best-time-to-buy-and-sell-stock-with-cooldown.js)|Medium|
+310|[Minimum Height Trees](./0310-minimum-height-trees.js)|Medium|
 315|[Count of Smaller Numbers After Self](./0315-count-of-smaller-numbers-after-self.js)|Hard|
 316|[Remove Duplicate Letters](./0316-remove-duplicate-letters.js)|Medium|
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