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heaps.js
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heaps.js
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/*---------Binary Heaps -------------------------
MaxBinaryHeap - parent nodes are always learger than child nodes
MinBinaryHeap - Parent nodes are always smaller than child nodes
- Just like Binary Trees, each nodes can have atmost two children
- the children has to be smaller than it's parent, doesnt matter right or left side
Heaps are used to implement Priority Queues and Grapgh Traversal
*/
class MaxBinaryHeap {
constructor() {
this.values = []
}
insert(element) {
this.values.push(element)
this.bubbleUp()
}
bubbleUp() {
let idx = this.values.length - 1
const element = this.values[idx]
while(idx > 0) {
let parentIdx = Math.floor((idx - 1)/2)
let parent = this.values[parentIdx]
if(element <= parent) break
this.values[parentIdx] = element
this.values[idx] = parent
idx = parentIdx
}
}
extractMax() {
const max = this.values[0]
const end = this.values.pop()
if(this.values.length > 0) {
this.values[0] = end
this.sinkDown()
}
return max
}
sinkDown() {
let idx = 0
const length = this.values.length
const element = this.values[0]
while(true) {
let leftChildIdx = 2 * idx + 1
let rightChildIdx = 2 * idx + 2
let leftChild, rightChild
let swap = null
if(leftChildIdx < length) {
leftChild = this.values[leftChildIdx]
if(leftChild > element) {
swap = leftChildIdx
}
}
if(rightChildIdx < length) {
rightChild = this.values[rightChildIdx]
if(
(swap === null && rightChild > element) ||
(swap !== null && rightChild > leftChild)
) {
swap = rightChildIdx
}
}
if(swap === null) break
this.values[idx] = this.values[swap]
this.values[swap] = element
idx = swap
}
}
}
let heap = new MaxBinaryHeap()
heap.insert(55)
heap.insert(37)
heap.insert(18)
console.log(heap.extractMax());
console.log(heap.extractMax());
console.log(heap.extractMax());
console.log(heap.values);
//Time Complexity
/*
Insertion - O(log n)
Removal - O(log n)
Search - O(n)
*/