update: new problem added

Author: ashokdey

src/_Problems_/max-product-of-3-numbers/index.js

@@ -0,0 +1,28 @@
+/**
+ * Given an array of numbers where the length can atmost be 10^4
+ * Find the maximum product of 3 numbers
+ * Samples:
+ * [1, 2, 3] - 6
+ * [-10, 10, 2, 3] - 60
+ * [-10, -10, 2, 3] - 300
+ */
+
+/** The following solution is O(nlogn) because of sorting */
+function maxProductof3Numbers(arr) {
+  if (!Array.isArray(arr)) {
+    throw new Error('Invalid Argument');
+  }
+
+  // sort the array
+  arr.sort((a, b) => a - b);
+
+  const n = arr.length;
+
+  // when the numbers are all positive
+  const p1 = arr[n - 1] * arr[n - 2] * arr[n - 3];
+
+  // considering -ve numbers, 2 -ve on multiplication becomes +ve
+  const p2 = arr[0] * arr[1] * arr[n - 1];
+
+  return p1 > p2 ? p1 : p2;
+}