Add solution #978

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,059 LeetCode solutions in JavaScript
+# 1,060 LeetCode solutions in JavaScript
 
 [https://leetcode.com/](https://leetcode.com/)
 
@@ -786,6 +786,7 @@
 975|[Odd Even Jump](./solutions/0975-odd-even-jump.js)|Hard|
 976|[Largest Perimeter Triangle](./solutions/0976-largest-perimeter-triangle.js)|Easy|
 977|[Squares of a Sorted Array](./solutions/0977-squares-of-a-sorted-array.js)|Easy|
+978|[Longest Turbulent Subarray](./solutions/0978-longest-turbulent-subarray.js)|Medium|
 985|[Sum of Even Numbers After Queries](./solutions/0985-sum-of-even-numbers-after-queries.js)|Easy|
 989|[Add to Array-Form of Integer](./solutions/0989-add-to-array-form-of-integer.js)|Easy|
 994|[Rotting Oranges](./solutions/0994-rotting-oranges.js)|Medium|

solutions/0978-longest-turbulent-subarray.js

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+/**
+ * 978. Longest Turbulent Subarray
+ * https://leetcode.com/problems/longest-turbulent-subarray/
+ * Difficulty: Medium
+ *
+ * Given an integer array arr, return the length of a maximum size turbulent subarray of arr.
+ *
+ * A subarray is turbulent if the comparison sign flips between each adjacent pair of elements
+ * in the subarray.
+ *
+ * More formally, a subarray [arr[i], arr[i + 1], ..., arr[j]] of arr is said to be turbulent
+ * if and only if:
+ * - For i <= k < j:
+ *   - arr[k] > arr[k + 1] when k is odd, and
+ *   - arr[k] < arr[k + 1] when k is even.
+ * - Or, for i <= k < j:
+ *   - arr[k] > arr[k + 1] when k is even, and
+ *   - arr[k] < arr[k + 1] when k is odd.
+ */
+
+/**
+ * @param {number[]} arr
+ * @return {number}
+ */
+var maxTurbulenceSize = function(arr) {
+  let result = 1;
+  let inc = 1;
+  let dec = 1;
+
+  for (let i = 1; i < arr.length; i++) {
+    if (arr[i] > arr[i - 1]) {
+      inc = dec + 1;
+      dec = 1;
+    } else if (arr[i] < arr[i - 1]) {
+      dec = inc + 1;
+      inc = 1;
+    } else {
+      inc = 1;
+      dec = 1;
+    }
+    result = Math.max(result, inc, dec);
+  }
+
+  return result;
+};