Implementation of max heap in Golang

maxheap.go

// Max Heap implementation
// We will be performing following operations on the max heap
// a) Add a new element (add)
// b) Fetch top element (peek)
// c) Delete top element (pop)
package main

import "fmt"

type maxHeap struct {
	// Create a complete binary tree using an array
	// Then use the binary tree to construct a Heap
	heap []int
	// the number of elements is needed when instantiating an array
	// heapSize records the size of the array
	heapSize int
	// realSize records the number of elements in the Heap
	realSize int
}

func (this *maxHeap) initialize(size int) {
	this.heapSize = size + 1
	this.heap = make([]int, this.heapSize)
	// To better track the indices of the binary tree,
	// we will not use the 0-th element in the array heap
}

func (this *maxHeap) add(element int) {
	this.realSize++
	// If the number of elements in the Heap exceeds the preset heapSize
	// print "Added too many elements" and return
	if this.realSize >= this.heapSize {
		fmt.Println("Added too many elements!")
		this.realSize--
		return
	}
	// Add the element into the array
	this.heap[this.realSize] = element
	// Index of the newly added element
	index := this.realSize
	// Parent node of the newly added element
	// Note if we use an array to represent the complete binary tree
	// and store the root node at index 1
	// index of the parent node of any node is [index of the node / 2]
	// index of the left child node is [index of the node * 2]
	// index of the right child node is [index of the node * 2 + 1]

	parent := index / 2
	// If the newly added element is larger than its parent node,
	// its value will be exchanged with that of the parent node
	for this.heap[index] > this.heap[parent] && index > 1 {
		temp := this.heap[index]
		this.heap[index] = this.heap[parent]
		this.heap[parent] = temp
		index = parent
		parent = index / 2
	}
}

// Get the top element of the Heap
func (this *maxHeap) peek() int {
	return this.heap[1]
}

// Delete the top element of the Heap
func (this *maxHeap) pop() int {
	// If the number of elements in the current Heap is 0,
	// print "Don't have any elements" and return a default value
	if this.realSize < 1 {
		fmt.Println("Don't have any element!")
		return 0
	} else {
		// When there are still elements in the Heap
		// realSize >= 1
		removedElement := this.heap[1]
		// Put the last element in the Heap to the top of Heap
		this.heap[1] = this.heap[this.realSize]
		this.realSize--
		index := 1
		// When the deleted element is not a leaf node
		for index <= this.realSize/2 {
			// the left child of the deleted element
			left := index * 2
			// the right child of the deleted element
			right := (index * 2) + 1
			// If the deleted element is smaller than the left or right child
			// its value needs to be exchanged with the larger value
			// of the left and right child
			if this.heap[index] < this.heap[left] || this.heap[index] < this.heap[right] {
				if this.heap[left] > this.heap[right] {
					temp := this.heap[left]
					this.heap[left] = this.heap[index]
					this.heap[index] = temp
					index = left
				} else {
					// this.heap[left] <= this.heap[right]
					temp := this.heap[right]
					this.heap[right] = this.heap[index]
					this.heap[index] = temp
					index = right
				}
			} else {
				break
			}
		}
		return removedElement
	}
}

func (this *maxHeap) print() {
	if this.realSize == 0 {
		fmt.Println("No element!")
	} else {
		var output []int
		for i := 1; i <= this.realSize; i++ {
			output = append(output, this.heap[i])
		}
		fmt.Println(output)
	}
}

// return the number of elements in the Heap
func (this *maxHeap) size() int {
	return this.realSize
}

func main() {
	var h maxHeap
	h.initialize(3)
	h.add(1)
	h.add(2)
	h.add(3)
	// [3,1,2]
	h.print()
	// 3
	fmt.Println(h.peek())
	// 3
	fmt.Println(h.pop())
	// 2
	fmt.Println(h.pop())
	// 1
	fmt.Println(h.pop())
	// No element
	h.print()
	// [4]
	h.add(4)
	// [5,4]
	h.add(5)
	// [10,4,5]
	h.add(10)
	// Added too many elements!
	h.add(11)
	// [10,4,5]
	h.print()
}

Try this code on https://go.dev/play/p/XjoE4JFupfZ