mirror of
https://github.com/krahets/hello-algo.git
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74 lines
1.8 KiB
C
74 lines
1.8 KiB
C
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/**
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* File: top_k.c
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* Created Time: 2023-10-26
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* Author: Krahets (krahets163.com)
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*/
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#include "my_heap.c"
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/* 元素入堆 */
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void pushMinHeap(MaxHeap *maxHeap, int val) {
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// 元素取反
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push(maxHeap, -val);
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}
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/* 元素出堆 */
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int popMinHeap(MaxHeap *maxHeap) {
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// 元素取反
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return -pop(maxHeap);
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}
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/* 访问堆顶元素 */
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int peekMinHeap(MaxHeap *maxHeap) {
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// 元素取反
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return -peek(maxHeap);
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}
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/* 取出堆中元素 */
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int *getMinHeap(MaxHeap *maxHeap) {
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// 将堆中所有元素取反并存入 res 数组
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int *res = (int *)malloc(maxHeap->size * sizeof(int));
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for (int i = 0; i < maxHeap->size; i++) {
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res[i] = -maxHeap->data[i];
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}
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return res;
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}
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// 基于堆查找数组中最大的 k 个元素的函数
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int *topKHeap(int *nums, int sizeNums, int k) {
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// 初始化小顶堆
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// 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
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int empty[0];
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MaxHeap *maxHeap = newMaxHeap(empty, 0);
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// 将数组的前 k 个元素入堆
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for (int i = 0; i < k; i++) {
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pushMinHeap(maxHeap, nums[i]);
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}
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// 从第 k+1 个元素开始,保持堆的长度为 k
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for (int i = k; i < sizeNums; i++) {
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// 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
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if (nums[i] > peekMinHeap(maxHeap)) {
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popMinHeap(maxHeap);
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pushMinHeap(maxHeap, nums[i]);
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}
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}
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int *res = getMinHeap(maxHeap);
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// 释放内存
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freeMaxHeap(maxHeap);
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return res;
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}
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/* Driver Code */
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int main() {
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int nums[] = {1, 7, 6, 3, 2};
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int k = 3;
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int sizeNums = sizeof(nums) / sizeof(nums[0]);
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int *res = topKHeap(nums, sizeNums, k);
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printf("最大的 %d 个元素为: ", k);
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printArray(res, k);
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free(res);
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return 0;
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}
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