Add solution #941

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# LeetCode solutions in JavaScript
+# 1,026 LeetCode solutions in JavaScript
 
 [https://leetcode.com/](https://leetcode.com/)
 
@@ -750,6 +750,7 @@
 938|[Range Sum of BST](./solutions/0938-range-sum-of-bst.js)|Easy|
 939|[Minimum Area Rectangle](./solutions/0939-minimum-area-rectangle.js)|Medium|
 940|[Distinct Subsequences II](./solutions/0940-distinct-subsequences-ii.js)|Hard|
+941|[Valid Mountain Array](./solutions/0941-valid-mountain-array.js)|Easy|
 966|[Vowel Spellchecker](./solutions/0966-vowel-spellchecker.js)|Medium|
 970|[Powerful Integers](./solutions/0970-powerful-integers.js)|Easy|
 976|[Largest Perimeter Triangle](./solutions/0976-largest-perimeter-triangle.js)|Easy|

solutions/0941-valid-mountain-array.js

@@ -0,0 +1,34 @@
+/**
+ * 941. Valid Mountain Array
+ * https://leetcode.com/problems/valid-mountain-array/
+ * Difficulty: Easy
+ *
+ * Given an array of integers arr, return true if and only if it is a valid mountain array.
+ *
+ * Recall that arr is a mountain array if and only if:
+ * - arr.length >= 3
+ * - There exists some i with 0 < i < arr.length - 1 such that:
+ *   - arr[0] < arr[1] < ... < arr[i - 1] < arr[i]
+ *   - arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
+ */
+
+/**
+ * @param {number[]} arr
+ * @return {boolean}
+ */
+var validMountainArray = function(arr) {
+  if (arr.length < 3) return false;
+
+  const peakIndex = arr.indexOf(Math.max(...arr));
+  if (peakIndex === 0 || peakIndex === arr.length - 1) return false;
+
+  for (let i = 1; i < peakIndex; i++) {
+    if (arr[i] <= arr[i - 1]) return false;
+  }
+
+  for (let i = peakIndex + 1; i < arr.length; i++) {
+    if (arr[i] >= arr[i - 1]) return false;
+  }
+
+  return true;
+};