Update 0239-sliding-window-maximum.js

Author: andynullwong

javascript/0239-sliding-window-maximum.js

@@ -80,3 +80,60 @@ var maxSlidingWindow = function (nums, k) {
     }
     return output;
 };
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+
+// Deque Implementation using Lazy Deletion
+class LazyDeletionDeque {
+    constructor() {
+        this.deque = [];
+        this.leftIdx = 0;
+    }
+
+    isEmpty = () => {
+        return this.deque.length === this.leftIdx;
+    };
+    push = (num) => {
+        this.deque.push(num);
+    };
+    popFront = () => {
+        this.leftIdx++;
+    };
+    popBack = () => {
+        !this.isEmpty() && this.deque.pop();
+    };
+    front = () => {
+        return this.deque[this.leftIdx];
+    };
+    back = () => {
+        return this.deque[this.deque.length - 1];
+    };
+}
+
+var maxSlidingWindowWithLazyDeletionDeque = function (nums, k) {
+    const deque = new LazyDeletionDeque();
+    const answer = [];
+    let leftWindow = 0;
+    for (let rightWindow = 0; rightWindow < nums.length; rightWindow++) {
+        const rightNum = nums[rightWindow];
+        while (!deque.isEmpty() && rightNum > deque.back()) {
+            deque.popBack();
+        }
+        deque.push(rightNum);
+
+        if (rightWindow >= k - 1) {
+            const dequeFront = deque.front();
+            const leftNum = nums[leftWindow];
+            if (leftNum === dequeFront) {
+                deque.popFront();
+            }
+            answer.push(dequeFront);
+            leftWindow++;
+        }
+    }
+    return answer;
+};