74 lines
2.0 KiB
C
74 lines
2.0 KiB
C
/**
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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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/* Push the element into heap */
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void pushMinHeap(MaxHeap *maxHeap, int val) {
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// Negate elements
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push(maxHeap, -val);
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}
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/* Element exits heap */
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int popMinHeap(MaxHeap *maxHeap) {
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// Negate elements
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return -pop(maxHeap);
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}
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/* Access heap top element */
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int peekMinHeap(MaxHeap *maxHeap) {
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// Negate elements
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return -peek(maxHeap);
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}
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/* Remove elements from the heap */
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int *getMinHeap(MaxHeap *maxHeap) {
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// Negate all elements in the heap and store them in the res array
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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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// Function to find the largest k elements in an array based on heap
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int *topKHeap(int *nums, int sizeNums, int k) {
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// Initialize min-heap
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// Please note: We negate all elements in the heap to simulate a min-heap using a max-heap
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int *empty = (int *)malloc(0);
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MaxHeap *maxHeap = newMaxHeap(empty, 0);
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// Enter the first k elements of the array into the heap
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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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// From the k+1th element, keep the heap length as k
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for (int i = k; i < sizeNums; i++) {
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// If the current element is larger than the heap top element, remove the heap top element and enter the current element into the heap
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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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// Free memory
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delMaxHeap(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("The largest %d elements are: ", 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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