Add solution #447

Author: JoshCrozier

README.md

@@ -355,6 +355,7 @@
 443|[String Compression](./0443-string-compression.js)|Medium|
 445|[Add Two Numbers II](./0445-add-two-numbers-ii.js)|Medium|
 446|[Arithmetic Slices II - Subsequence](./0446-arithmetic-slices-ii-subsequence.js)|Hard|
+447|[Number of Boomerangs](./0447-number-of-boomerangs.js)|Medium|
 448|[Find All Numbers Disappeared in an Array](./0448-find-all-numbers-disappeared-in-an-array.js)|Easy|
 450|[Delete Node in a BST](./0450-delete-node-in-a-bst.js)|Medium|
 451|[Sort Characters By Frequency](./0451-sort-characters-by-frequency.js)|Medium|

solutions/0447-number-of-boomerangs.js

@@ -0,0 +1,33 @@
+/**
+ * 447. Number of Boomerangs
+ * https://leetcode.com/problems/number-of-boomerangs/
+ * Difficulty: Medium
+ *
+ * You are given n points in the plane that are all distinct, where points[i] = [xi, yi].
+ * A boomerang is a tuple of points (i, j, k) such that the distance between i and j equals
+ * the distance between i and k (the order of the tuple matters).
+ *
+ * Return the number of boomerangs.
+ */
+
+/**
+ * @param {number[][]} points
+ * @return {number}
+ */
+var numberOfBoomerangs = function(points) {
+  let count = 0;
+
+  for (let i = 0; i < points.length; i++) {
+    const distances = new Map();
+    for (let j = 0; j < points.length; j++) {
+      if (i === j) continue;
+      const d = (points[i][0] - points[j][0]) ** 2 + (points[i][1] - points[j][1]) ** 2;
+      distances.set(d, (distances.get(d) || 0) + 1);
+    }
+    for (const d of distances.values()) {
+      if (d > 1) count += d * (d - 1);
+    }
+  }
+
+  return count;
+};