Heap Concept Structure and Properties in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the index of the left child in a heap array.

DSA Javascript

function leftChildIndex(parentIndex) {
  return 2 * parentIndex [1] 1;
}

Drag options to blanks, or click blank then click option'

A+

B/

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction instead of addition.

Using multiplication instead of addition.

Using division which is incorrect here.

The left child index in a heap array is calculated as 2 * parentIndex + 1.

2fill in blank

medium

Complete the code to get the index of the parent node in a heap array.

DSA Javascript

function parentIndex(childIndex) {
  return Math.floor((childIndex [1] 1) / 2);
}

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A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Adding 1 instead of subtracting 1.

Not using floor which causes wrong index.

Using multiplication or division incorrectly.

The parent index is calculated as floor((childIndex - 1) / 2) in a heap array.

3fill in blank

hard

Fix the error in the code to check if a node has a right child in the heap array.

DSA Javascript

function hasRightChild(index, heapSize) {
  return (2 * index + [1]) < heapSize;
}

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A-1

B0

C1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 2 for right child index.

Using 0 or negative numbers which are invalid here.

The right child index is 2 * index + 2, so we check if this is less than heapSize.

4fill in blank

hard

Fill both blanks to create a function that swaps two elements in a heap array.

DSA Javascript

function swap(heap, i, j) {
  const temp = heap[1];
  heap[2] = heap[j];
  heap[j] = temp;
}

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A[i]

B[j]

C.i

D.j

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot notation instead of bracket notation.

Mixing indices between temp and heap assignments.

To swap elements, use bracket notation with indices: heap[i] and heap[j].

5fill in blank

hard

Fill all three blanks to complete the siftDown function that maintains the heap property.

DSA Javascript

function siftDown(heap, index, heapSize) {
  let largest = index;
  const left = 2 * index + [1];
  const right = 2 * index + [2];

  if (left < heapSize && heap[left] > heap[[3]]) {
    largest = left;
  }

  if (right < heapSize && heap[right] > heap[largest]) {
    largest = right;
  }

  if (largest !== index) {
    swap(heap, index, largest);
    siftDown(heap, largest, heapSize);
  }
}

Drag options to blanks, or click blank then click option'

A1

B2

Cindex

Dlargest

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up left and right child offsets.

Comparing with largest instead of index in first if condition.

Left child index is 2*index+1, right child is 2*index+2, and compare heap[left] with heap[index].