Max Heap in JavaScript – GeeksforGeeks
class MaxHeap {
constructor() {
this.heap = [];
}
getLeftChildIndex(parentIndex) { return 2 * parentIndex + 1; }
getRightChildIndex(parentIndex) { return 2 * parentIndex + 2; }
getParentIndex(childIndex) {
return Math.floor((childIndex - 1) / 2);
}
hasLeftChild(index) {
return this.getLeftChildIndex(index) < this.heap.length;
}
hasRightChild(index) {
return this.getRightChildIndex(index) < this.heap.length;
}
hasParent(index) {
return this.getParentIndex(index) >= 0;
}
leftChild(index) {
return this.heap[this.getLeftChildIndex(index)];
}
rightChild(index) {
return this.heap[this.getRightChildIndex(index)];
}
parent(index) {
return this.heap[this.getParentIndex(index)];
}
swap(indexOne, indexTwo) {
const temp = this.heap[indexOne];
this.heap[indexOne] = this.heap[indexTwo];
this.heap[indexTwo] = temp;
}
peek() {
if (this.heap.length === 0) {
return null;
}
return this.heap[0];
}
remove() {
if (this.heap.length === 0) {
return null;
}
const item = this.heap[0];
this.heap[0] = this.heap[this.heap.length - 1];
this.heap.pop();
this.heapifyDown();
return item;
}
add(item) {
this.heap.push(item);
this.heapifyUp();
}
heapifyUp() {
let index = this.heap.length - 1;
while (this.hasParent(index) && this.parent(index) < this.heap[index]) {
this.swap(this.getParentIndex(index), index);
index = this.getParentIndex(index);
}
}
heapifyDown() {
let index = 0;
while (this.hasLeftChild(index)) {
let largerChildIndex = this.getLeftChildIndex(index);
if (this.hasRightChild(index) && this.rightChild(index) > this.leftChild(index)) {
largerChildIndex = this.getRightChildIndex(index);
}
if (this.heap[index] > this.heap[largerChildIndex]) {
break;
} else {
this.swap(index, largerChildIndex);
}
index = largerChildIndex;
}
}
printHeap() {
var heap =` ${this.heap[0]} `
for(var i = 1; i<this.heap.length;i++) {
heap += ` ${this.heap[i]} `;
}
console.log(heap);
}
}
var heap = new MaxHeap();
heap.add(10);
heap.add(15);
heap.add(30);
heap.add(40);
heap.add(50);
heap.add(100);
heap.add(40);
heap.printHeap();
console.log(heap.peek());
console.log(heap.remove());
heap.printHeap();
class MaxHeap {
constructor() {
this.heap = [];
}
getLeftChildIndex(parentIndex) { return 2 * parentIndex + 1; }
getRightChildIndex(parentIndex) { return 2 * parentIndex + 2; }
getParentIndex(childIndex) {
return Math.floor((childIndex - 1) / 2);
}
hasLeftChild(index) {
return this.getLeftChildIndex(index) < this.heap.length;
}
hasRightChild(index) {
return this.getRightChildIndex(index) < this.heap.length;
}
hasParent(index) {
return this.getParentIndex(index) >= 0;
}
leftChild(index) {
return this.heap[this.getLeftChildIndex(index)];
}
rightChild(index) {
return this.heap[this.getRightChildIndex(index)];
}
parent(index) {
return this.heap[this.getParentIndex(index)];
}
swap(indexOne, indexTwo) {
const temp = this.heap[indexOne];
this.heap[indexOne] = this.heap[indexTwo];
this.heap[indexTwo] = temp;
}
peek() {
if (this.heap.length === 0) {
return null;
}
return this.heap[0];
}
remove() {
if (this.heap.length === 0) {
return null;
}
const item = this.heap[0];
this.heap[0] = this.heap[this.heap.length - 1];
this.heap.pop();
this.heapifyDown();
return item;
}
add(item) {
this.heap.push(item);
this.heapifyUp();
}
heapifyUp() {
let index = this.heap.length - 1;
while (this.hasParent(index) && this.parent(index) < this.heap[index]) {
this.swap(this.getParentIndex(index), index);
index = this.getParentIndex(index);
}
}
heapifyDown() {
let index = 0;
while (this.hasLeftChild(index)) {
let largerChildIndex = this.getLeftChildIndex(index);
if (this.hasRightChild(index) && this.rightChild(index) > this.leftChild(index)) {
largerChildIndex = this.getRightChildIndex(index);
}
if (this.heap[index] > this.heap[largerChildIndex]) {
break;
} else {
this.swap(index, largerChildIndex);
}
index = largerChildIndex;
}
}
printHeap() {
var heap =` ${this.heap[0]} `
for(var i = 1; i<this.heap.length;i++) {
heap += ` ${this.heap[i]} `;
}
console.log(heap);
}
}
var heap = new MaxHeap();
heap.add(10);
heap.add(15);
heap.add(30);
heap.add(40);
heap.add(50);
heap.add(100);
heap.add(40);
heap.printHeap();
console.log(heap.peek());
console.log(heap.remove());
heap.printHeap();
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