Add JavaScript and TypeScript code of top_k and update some code style (#686)

* Update JS and TS code style

* Add JavaScript and TypeScript code of top_k

* Update top_k.ts

* Apply suggestions from code review

Co-authored-by: Justin Tse <xiefahit@gmail.com>

* Apply suggestions from code review

Co-authored-by: Justin Tse <xiefahit@gmail.com>

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/javascript/chapter_heap/my_heap.js

@@ -115,6 +115,11 @@ class MaxHeap {
     print() {
         printHeap(this.#maxHeap);
     }
+
+    /* 取出堆中元素 */
+    getMaxHeap() {
+        return this.#maxHeap;
+    }
 }
 
 /* Driver Code */
@@ -145,3 +150,8 @@ console.log(`\n堆元素数量为 ${size}`);
 /* 判断堆是否为空 */
 let isEmpty = maxHeap.isEmpty();
 console.log(`\n堆是否为空 ${isEmpty}`);
+
+
+module.exports = {
+    MaxHeap,
+};

codes/javascript/chapter_heap/top_k.js

@@ -0,0 +1,34 @@
+/**
+ * File: top_k.js
+ * Created Time: 2023-08-13
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { MaxHeap } = require('./my_heap');
+
+/* 基于堆查找数组中最大的 k 个元素 */
+function top_k_heap(nums, k) {
+    // 使用大顶堆 MaxHeap，对数组 nums 取相反数
+    const invertedNums = nums.map(num => -num);
+    // 将数组的前 k 个元素入堆
+    const heap = new MaxHeap(invertedNums.slice(0, k));
+    // 从第 k+1 个元素开始，保持堆的长度为 k
+    for (let i = k; i < invertedNums.length; i++) {
+        // 若当前元素小于堆顶元素，则将堆顶元素出堆、当前元素入堆
+        if (invertedNums[i] < heap.peek()) {
+            heap.pop();
+            heap.push(invertedNums[i]);
+        }
+    }
+    // 取出堆中元素
+    const maxHeap = heap.getMaxHeap();
+    // 对堆中元素取相反数
+    const invertedMaxHeap = maxHeap.map(num => -num);
+    return invertedMaxHeap;
+}
+
+/* Driver Code */
+const nums = [1, 7, 6, 3, 2];
+const k = 3;
+const res = top_k_heap(nums, k);
+console.log(`最大的 ${k} 个元素为`, res);