2017-09-29 23:16:15 +02:00
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/*
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2020-05-05 17:41:32 +05:30
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* Build a max heap out of the array. A heap is a specialized tree like
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* data structure that satisfies the heap property. The heap property
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* for max heap is the following: "if P is a parent node of C, then the
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* key (the value) of node P is greater than the key of node C"
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* Source: https://en.wikipedia.org/wiki/Heap_(data_structure)
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*/
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/* eslint no-extend-native: ["off", { "exceptions": ["Object"] }] */
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2017-09-29 23:16:15 +02:00
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Array.prototype.heapify = function (index, heapSize) {
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2020-05-03 09:05:12 +02:00
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let largest = index
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const leftIndex = 2 * index + 1
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const rightIndex = 2 * index + 2
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2017-09-29 23:16:15 +02:00
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if (leftIndex < heapSize && this[leftIndex] > this[largest]) {
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2020-05-03 09:05:12 +02:00
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largest = leftIndex
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2017-09-29 23:16:15 +02:00
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}
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if (rightIndex < heapSize && this[rightIndex] > this[largest]) {
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2020-05-03 09:05:12 +02:00
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largest = rightIndex
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2017-09-29 23:16:15 +02:00
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}
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if (largest !== index) {
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2020-05-03 09:05:12 +02:00
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const temp = this[largest]
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this[largest] = this[index]
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this[index] = temp
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2017-09-29 23:16:15 +02:00
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2020-05-03 09:05:12 +02:00
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this.heapify(largest, heapSize)
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2017-09-29 23:16:15 +02:00
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}
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2020-05-03 09:05:12 +02:00
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}
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2017-09-29 23:16:15 +02:00
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/*
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2020-05-05 17:41:32 +05:30
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* Heap sort sorts an array by building a heap from the array and
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* utilizing the heap property.
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* For more information see: https://en.wikipedia.org/wiki/Heapsort
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*/
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2021-10-11 12:29:03 +02:00
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export function heapSort (items) {
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2020-05-03 09:05:12 +02:00
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const length = items.length
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2017-09-29 23:16:15 +02:00
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2018-03-31 00:01:22 +02:00
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for (let i = Math.floor(length / 2) - 1; i > -1; i--) {
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2020-05-03 09:05:12 +02:00
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items.heapify(i, length)
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2017-09-29 23:16:15 +02:00
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}
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2020-05-03 09:05:12 +02:00
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for (let j = length - 1; j > 0; j--) {
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const tmp = items[0]
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items[0] = items[j]
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items[j] = tmp
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items.heapify(0, j)
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2017-09-29 23:16:15 +02:00
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}
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2020-05-03 09:05:12 +02:00
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return items
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2017-09-29 23:16:15 +02:00
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}
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2020-05-03 09:05:12 +02:00
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// Implementation of heapSort
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2017-09-29 23:16:15 +02:00
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2021-10-11 12:29:03 +02:00
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// const ar = [5, 6, 7, 8, 1, 2, 12, 14]
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// heapSort(ar)
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