59 lines
1.6 KiB
JavaScript
59 lines
1.6 KiB
JavaScript
/**
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* File: top_k.js
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* Created Time: 2023-08-13
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* Author: Justin (xiefahit@gmail.com)
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*/
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const { MaxHeap } = require('./my_heap');
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/* Push the element into heap */
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function pushMinHeap(maxHeap, val) {
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// Negate elements
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maxHeap.push(-val);
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}
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/* Element exits heap */
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function popMinHeap(maxHeap) {
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// Negate elements
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return -maxHeap.pop();
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}
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/* Access heap top element */
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function peekMinHeap(maxHeap) {
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// Negate elements
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return -maxHeap.peek();
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}
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/* Remove elements from the heap */
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function getMinHeap(maxHeap) {
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// Negate elements
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return maxHeap.getMaxHeap().map((num) => -num);
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}
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/* Using heap to find the largest k elements in an array */
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function topKHeap(nums, 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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const maxHeap = new MaxHeap([]);
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// Enter the first k elements of the array into the heap
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for (let 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 (let i = k; i < nums.length; 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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// Return the element from the heap
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return getMinHeap(maxHeap);
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}
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/* Driver Code */
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const nums = [1, 7, 6, 3, 2];
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const k = 3;
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const res = topKHeap(nums, k);
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console.log(`最大的 ${k} 个元素为`, res);
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