Add solution #396

Author: JoshCrozier

README.md

@@ -314,6 +314,7 @@
 393|[UTF-8 Validation](./0393-utf-8-validation.js)|Medium|
 394|[Decode String](./0394-decode-string.js)|Medium|
 395|[Longest Substring with At Least K Repeating Characters](./0395-longest-substring-with-at-least-k-repeating-characters.js)|Medium|
+396|[Rotate Function](./0396-rotate-function.js)|Medium|
 399|[Evaluate Division](./0399-evaluate-division.js)|Medium|
 404|[Sum of Left Leaves](./0404-sum-of-left-leaves.js)|Easy|
 405|[Convert a Number to Hexadecimal](./0405-convert-a-number-to-hexadecimal.js)|Easy|

solutions/0396-rotate-function.js

@@ -0,0 +1,32 @@
+/**
+ * 396. Rotate Function
+ * https://leetcode.com/problems/rotate-function/
+ * Difficulty: Medium
+ *
+ * You are given an integer array nums of length n.
+ *
+ * Assume arrk to be an array obtained by rotating nums by k positions clock-wise.
+ * We define the rotation function F on nums as follow:
+ * - F(k) = 0 * arrk[0] + 1 * arrk[1] + ... + (n - 1) * arrk[n - 1].
+ *
+ * Return the maximum value of F(0), F(1), ..., F(n-1).
+ *
+ * The test cases are generated so that the answer fits in a 32-bit integer.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var maxRotateFunction = function(nums) {
+  const sum = nums.reduce((a, b) => a + b, 0);
+  let current = nums.reduce((total, n, i) => total + i * n, 0);
+  let result = current;
+
+  for (let i = 1; i < nums.length; i++) {
+    current = current + sum - nums.length * nums[nums.length - i];
+    result = Math.max(result, current);
+  }
+
+  return result;
+};