Build Heap from Array Heapify in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the index of the last non-leaf node in the heap array.

DSA Typescript

const lastNonLeaf = Math.floor((arr.length - 2) / [1]);

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A2

B3

C1

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using length / 2 instead of (length - 2) / 2

Using 3 instead of 2 as divisor

Confusing leaf nodes with non-leaf nodes

In a binary heap stored as an array, the last non-leaf node is at index floor((n-2)/2).

2fill in blank

medium

Complete the code to swap two elements in the array during heapify.

DSA Typescript

const temp = arr[i]; arr[i] = arr[[1]]; arr[[1]] = temp;

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Aparent

Bsmallest

Clargest

Dchild

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping with 'smallest' instead of 'largest'

Swapping with 'parent' which is the current node itself

Using an undefined variable

During heapify, we swap the current node with the largest child to maintain the heap property.

3fill in blank

hard

Fix the error in the heapify function's recursive call to maintain heap property.

DSA Typescript

if (largest !== i) { heapify(arr, arr.length, [1]); }

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Alargest

Bi

C0

Darr.length

Attempts:

3 left

💡 Hint

Common Mistakes

Calling heapify with 'i' which causes infinite recursion

Calling heapify with 0 which restarts from root unnecessarily

Using arr.length as index which is out of bounds

After swapping, heapify must be called recursively on the index 'largest' to fix the subtree.

4fill in blank

hard

Fill both blanks to complete the loop that builds the heap from the array.

DSA Typescript

for (let i = [1]; i >= 0; i[2]) { heapify(arr, arr.length, i); }

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AMath.floor(arr.length / 2) - 1

B0

C--

D++

Attempts:

3 left

💡 Hint

Common Mistakes

Starting from 0 and incrementing instead of decrementing

Using ++ instead of -- in the loop

Starting from arr.length instead of last non-leaf node

The build heap process starts from the last non-leaf node down to the root, decrementing i each time.

5fill in blank

hard

Fill all three blanks to complete the heapify function header and left child calculation.

DSA Typescript

function heapify(arr: number[], n: number, [1]: number) {
  const left = 2 * [2] + [3];
  // rest of heapify code
}

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Ai

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 instead of 1 for left child offset

Using different variable names inconsistently

Confusing left child with right child index

The heapify function uses 'i' as the current index, and left child is at 2*i + 1 in a binary heap.