Add solution #239

Author: JoshCrozier

README.md

@@ -215,6 +215,7 @@
 236|[Lowest Common Ancestor of a Binary Tree](./0236-lowest-common-ancestor-of-a-binary-tree.js)|Medium|
 237|[Delete Node in a Linked List](./0237-delete-node-in-a-linked-list.js)|Easy|
 238|[Product of Array Except Self](./0238-product-of-array-except-self.js)|Medium|
+239|[Sliding Window Maximum](./0239-sliding-window-maximum.js)|Hard|
 242|[Valid Anagram](./0242-valid-anagram.js)|Easy|
 257|[Binary Tree Paths](./0257-binary-tree-paths.js)|Easy|
 258|[Add Digits](./0258-add-digits.js)|Easy|

solutions/0239-sliding-window-maximum.js

@@ -0,0 +1,36 @@
+/**
+ * 239. Sliding Window Maximum
+ * https://leetcode.com/problems/sliding-window-maximum/
+ * Difficulty: Hard
+ *
+ * You are given an array of integers nums, there is a sliding window of size k which is moving
+ * from the very left of the array to the very right. You can only see the k numbers in the
+ * window. Each time the sliding window moves right by one position.
+ *
+ * Return the max sliding window.
+ */
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var maxSlidingWindow = function(nums, k) {
+  const result = [];
+  const queue = [];
+
+  for (let i = 0; i < nums.length; i++) {
+    while (queue.length && queue[0] < i - k + 1) {
+      queue.shift();
+    }
+    while (queue.length && nums[queue[queue.length - 1]] < nums[i]) {
+      queue.pop();
+    }
+    queue.push(i);
+    if (i >= k - 1) {
+      result.push(nums[queue[0]]);
+    }
+  }
+
+  return result;
+};