let arrayLength = 0

/* to create MAX array */

function heapRoot (input, i) {

const left = 2 * i + 1

const right = 2 * i + 2

let max = i

if (left < arrayLength && input[left] > input[max]) {

max = left

}

if (right < arrayLength && input[right] > input[max]) {

max = right

}

if (max !== i) {

swap(input, i, max)

heapRoot(input, max)

}

}

function swap (input, indexA, indexB) {

[input[indexA], input[indexB]] = [input[indexB], input[indexA]]

}

export function heapSort (input) {

arrayLength = input.length

for (let i = Math.floor(arrayLength / 2); i >= 0; i -= 1) {

heapRoot(input, i)

}

for (let i = input.length - 1; i > 0; i--) {

swap(input, 0, i)

arrayLength--

heapRoot(input, 0)

}

return input

}