Heap sort in Go

heapsort.go

package main

import (
	"fmt"
)

func swap(a, b *int) {
	t := *a
	*a = *b
	*b = t
}

func heapify(arr []int, i int) {
	n := len(arr)
	largest := i
	l := 2*i + 1
	r := 2*i + 2

	if l < n && arr[l] > arr[largest] {
		largest = l
	}

	if r < n && arr[r] > arr[largest] {
		largest = r
	}

	if largest != i {
		swap(&arr[i], &arr[largest])
		heapify(arr, largest)
	}
}

func heapSort(arr []int) {
	n := len(arr)

	for i := n/2 - 1; i >= 0; i-- {
		heapify(arr, i)
	}

	for i := n - 1; i > 0; i-- {
		swap(&arr[0], &arr[i])
		heapify(arr[:i], 0)
	}
}

func main() {
	arr := []int{1, 3, 5, 4, 6, 13, 10, 9, 8, 15, 17}
	heapSort(arr)

	fmt.Println(arr)
}