feat: add top_k.c and refactor top_k.js (#889)

* Add top_k.c based on my_heap.c

* Improve the implementation of top_k.js

* Add a comment to top_k

codes/c/chapter_heap/top_k.c

@@ -0,0 +1,73 @@
+/**
+ * File: top_k.c
+ * Created Time: 2023-10-26
+ * Author: Krahets (krahets163.com)
+ */
+
+#include "my_heap.c"
+
+/* 元素入堆 */
+void pushMinHeap(MaxHeap *maxHeap, int val) {
+    // 元素取反
+    push(maxHeap, -val);
+}
+
+/* 元素出堆 */
+int popMinHeap(MaxHeap *maxHeap) {
+    // 元素取反
+    return -pop(maxHeap);
+}
+
+/* 访问堆顶元素 */
+int peekMinHeap(MaxHeap *maxHeap) {
+    // 元素取反
+    return -peek(maxHeap);
+}
+
+/* 取出堆中元素 */
+int *getMinHeap(MaxHeap *maxHeap) {
+    // 将堆中所有元素取反并存入 res 数组
+    int *res = (int *)malloc(maxHeap->size * sizeof(int));
+    for (int i = 0; i < maxHeap->size; i++) {
+        res[i] = -maxHeap->data[i];
+    }
+    return res;
+}
+
+// 基于堆查找数组中最大的 k 个元素的函数
+int *topKHeap(int *nums, int sizeNums, int k) {
+    // 初始化小顶堆
+    // 请注意：我们将堆中所有元素取反，从而用大顶堆来模拟小顶堆
+    int empty[0];
+    MaxHeap *maxHeap = newMaxHeap(empty, 0);
+    // 将数组的前 k 个元素入堆
+    for (int i = 0; i < k; i++) {
+        pushMinHeap(maxHeap, nums[i]);
+    }
+    // 从第 k+1 个元素开始，保持堆的长度为 k
+    for (int i = k; i < sizeNums; i++) {
+        // 若当前元素大于堆顶元素，则将堆顶元素出堆、当前元素入堆
+        if (nums[i] > peekMinHeap(maxHeap)) {
+            popMinHeap(maxHeap);
+            pushMinHeap(maxHeap, nums[i]);
+        }
+    }
+    int *res = getMinHeap(maxHeap);
+    // 释放内存
+    freeMaxHeap(maxHeap);
+    return res;
+}
+
+/* Driver Code */
+int main() {
+    int nums[] = {1, 7, 6, 3, 2};
+    int k = 3;
+    int sizeNums = sizeof(nums) / sizeof(nums[0]);
+
+    int *res = topKHeap(nums, sizeNums, k);
+    printf("最大的 %d 个元素为: ", k);
+    printArray(res, k);
+
+    free(res);
+    return 0;
+}