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How to build a heap in JavaScript?

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Wissam answered on May 10, 2022 Popularity 10/10 Helpfulness 4/10

answer How to build a heap in JavaScript?

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How to build a heap in JavaScript?

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// Aim is to build a min-heap from an
// array of integers with support for following methods:
// buildHeap(array): to build the heap from array
// bubbleDown(currentIdx, endIdx, heap): to bubble an element down
// bubbleUp(currentIdx, heap): to bubble an element up
// peek(): returns min value without removing it
// remove(): removes min value
// insert(): inserts a new element into heap
class MinHeap {
  // Build heap using array of ints
  constructor(array) {
    this.heap = this.buildHeap(array);
  }
  // O(n) time | O(1) space
  buildHeap(array) {
    const firstParentIdx = Math.floor((array.length - 2) / 2);
    for (let currentIdx = firstParentIdx; currentIdx >= 0; currentIdx--) {
      this.bubbleDown(currentIdx, array.length - 1, array);
    }
    return array;
  }
  // O(log(n)) time | O(1) space
  bubbleDown(currentIdx, endIdx, heap) {
    let childOneIdx = currentIdx * 2 + 1;
    while (childOneIdx <= endIdx) {
      const childTwoIdx =
        currentIdx * 2 + 2 <= endIdx ? currentIdx * 2 + 2 : -1;
      let idxToSwap;
      if (childTwoIdx !== -1 && heap[childTwoIdx] < heap[childOneIdx]) {
        idxToSwap = childTwoIdx;
      } else {
        idxToSwap = childOneIdx;
      }
      if (heap[idxToSwap] < heap[currentIdx]) {
        this.swap(currentIdx, idxToSwap, heap);
        currentIdx = idxToSwap;
        childOneIdx = currentIdx * 2 + 1;
      } else {
        return;
      }
    }
  }
  // O(log(n)) time | O(1) space
  bubbleUp(currentIdx, heap) {
    let parentIdx = Math.floor((currentIdx - 1) / 2);
    while (currentIdx > 0 && heap[currentIdx] < heap[parentIdx]) {
      this.swap(currentIdx, parentIdx, heap);
      currentIdx = parentIdx;
      parentIdx = Math.floor((currentIdx - 1) / 2);
    }
  }
  // O(1) time | O(1) space
  peek() {
    return this.heap[0];
  }
  // O(log(n)) time | O(1) space
  remove() {
    this.swap(0, this.heap.length - 1, this.heap);
    const valueToRemove = this.heap.pop();
    this.bubbleDown(0, this.heap.length - 1, this.heap);
    return valueToRemove;
  }
  // O(log(n)) time | O(1) space
  insert(value) {
    this.heap.push(value);
    this.bubbleUp(this.heap.length - 1, this.heap);
  }
  swap(i, j, heap) {
    const temp = heap[i];
    heap[i] = heap[j];
    heap[j] = temp;
  }
}

Popularity 10/10 Helpfulness 4/10 Language javascript

Source: Grepper

Tags: build heap javascript min-heap

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Contributed on May 10 2022

Wissam

0 Answers Avg Quality 2/10

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heap javascript

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class Heap{
constructor(capacity, heap_type)
  {
  
  this.heap_type = heap_type;
    this.count = 0;
    this.capacity = capacity;
    this.array = [];
    
  }
  
 
  Parent()
  {
  if(i<= 0 || i>=this.count)
  {return -1;}
    
    return i-1/2;
    
  }

  
  LeftChildren(i)
  {
  
  left = 2*i +1;
   if(left >= this.count)
   {
   return -1;
   }
    
    return left;
  
  }
  
  
  GetMaximum()
  {
    
  if(this.count == 0)
  {
    return -1;
  }
    
    return this.array[0];
  
  }
  
  
  PercolateDown(i){
var i, r, max, temp;
 l = LeftChild(i);
    r = RightChild(i);
    
    
    if(l !=  -1 && this.array[r] > this.array[max])
    {
    max = r;
    }
    
    if(max != i)
    {
    temp = this.array[i];
      this.array[i] = this.array[max];
      max = r;
    
    }
    
    if(max != i){
      
      temp = this.array[i];
 
      this.array[i] = this.array[max];
      this.array[max] = temp;
  }
  PercolateDown(max);
  }
  
  DeleteMax()
  {
   if(this.count == 0) 
   {
   return -1;
   }
  
    
    data = this.array[0];
    this.array[0] = this.array[this.count-1];
    
    
    this.count --;
    PercolateDown(0);
    
    return data;
    
  
  }
  
  Insert(data)
  {
    
    i; 
    if(this.count == this.capacity)
    {
    
     ResizeHeap();
    
    }
    
    
    this.count++;
    
    
    
    while(i>=0 && data  >this.array[(i-1)/2]){
      this.array[i] = this.array[(i-1)/2];
      i = i-1/2;
    }
    
    this.array[i] = data;
    
  }
  
  
  ResizeHeap()
  {
this.array = [...this.array]
    if(this.array == null)
    {console.log("Memory Error)
            return;     
                 }
    
  
    
    for(i =0; i<this.capacity; i++)
    {
    this.array[i] = array_old[i];
    }
    
    this.capacity *=2;
    array_old =null
  }
  
  Heapsort(A, n)
  {
  
    h = new Heap(n,0);
    
    var old_size, i, temp;
    BuildHeap(h, A, n);
    
    old_size = h.count;
    for(i = n-1 ; i>0; i--)
    {
    temp = h.array[0];
      h.array[0] = h.array[h.count-1];
      h.count--;
      h.PercolateDown(0);
      
      
    }
    
    
    h.count = old_size;
    
  
  }
  
}

Popularity 10/10 Helpfulness 1/10 Language javascript

Source: Grepper

Tags: heap

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Contributed on Jul 25 2022

Javasper

0 Answers Avg Quality 2/10

what is a heap in javascript

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heap is a binary tree where each node is greater than both its leaves.
The tree itself is complete or nearly complete at all times,
so the heap is backed by a compact array.
When values are added or removed, the tree rotates until the value has 
sunk until its parent is greater, or floated until all children are less.

Popularity 9/10 Helpfulness 1/10 Language javascript

Source: Grepper

Tags: heap

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Contributed on Jul 21 2022

0xTony143

0 Answers Avg Quality 2/10

what is heap in javascript

Comment

-1

 heap is a binary tree where each node is greater than both its leaves.
 The tree itself is complete or nearly complete at all times,
 so the heap is backed by a compact array.
 When values are added or removed, the tree rotates until the value has 
 sunk until its parent is greater, or floated until all children are less.

Popularity 10/10 Helpfulness 1/10 Language javascript

Source: Grepper

Tags: heap

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Contributed on May 25 2022

Himanshu Jangid

0 Answers Avg Quality 2/10

How to build a heap in JavaScript?

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