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/*

* Build a max heap out of the array. A heap is a specialized tree like

* data structure that satisfies the heap property. The heap property

* for max heap is the following: "if P is a parent node of C, then the

* key (the value) of node P is greater than the key of node C"

* Source: https://en.wikipedia.org/wiki/Heap_(data_structure)

*/

/* eslint no-extend-native: ["off", { "exceptions": ["Object"] }] */

Array.prototype.heapify = function (index, heapSize) {

let largest = index

const leftIndex = 2 * index + 1

const rightIndex = 2 * index + 2

if (leftIndex < heapSize && this[leftIndex] > this[largest]) {

largest = leftIndex

}

if (rightIndex < heapSize && this[rightIndex] > this[largest]) {

largest = rightIndex

}

if (largest !== index) {

const temp = this[largest]

this[largest] = this[index]

this[index] = temp

this.heapify(largest, heapSize)

}

}

/*

* Heap sort sorts an array by building a heap from the array and

* utilizing the heap property.

* For more information see: https://en.wikipedia.org/wiki/Heapsort

*/

export function heapSort (items) {

const length = items.length

for (let i = Math.floor(length / 2) - 1; i > -1; i--) {

items.heapify(i, length)

}

for (let j = length - 1; j > 0; j--) {

const tmp = items[0]

items[0] = items[j]

items[j] = tmp

items.heapify(0, j)

}

return items

}

// Implementation of heapSort

// const ar = [5, 6, 7, 8, 1, 2, 12, 14]

// heapSort(ar)