Build Heap from Array Heapify in DSA C++ - 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 C++

int lastNonLeaf = (n [1] 2) - 1;

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

A/

B*

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication instead of division.

Forgetting to subtract 1 after division.

The last non-leaf node in a heap array of size n is at index (n / 2) - 1.

2fill in blank

medium

Complete the code to call heapify on each non-leaf node starting from the last non-leaf node.

DSA C++

for (int i = lastNonLeaf; i >= 0; i--) {
    heapify(arr, n, [1]);
}

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

Ai

Bn

C0

DlastNonLeaf

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the size n instead of the node index.

Passing 0 or lastNonLeaf instead of the current index.

We call heapify on each node index i from lastNonLeaf down to 0.

3fill in blank

hard

Fix the error in the heapify function call inside the buildHeap function.

DSA C++

void buildHeap(int arr[], int n) {
    int startIdx = (n / 2) - 1;
    for (int i = startIdx; i >= 0; i--) {
        heapify(arr, [1], i);
    }
}

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

Ai

Bn

CstartIdx

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the current index i as the size parameter.

Confusing the order of parameters in heapify.

heapify needs the size of the array n and the current index i to work correctly.

4fill in blank

hard

Fill both blanks to complete the heapify function's left and right child index calculations.

DSA C++

int left = 2 * [1] + [2];
int right = 2 * [1] + 2;

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

Ai

B1

C0

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 instead of 1 for left child offset.

Using n or other variables instead of i.

Left child index is 2*i + 1 and right child index is 2*i + 2 in a zero-indexed heap array.

5fill in blank

hard

Fill all three blanks to complete the heapify function's swap and recursive call.

DSA C++

if (largest != [1]) {
    std::swap(arr[[2]], arr[[3]]);
    heapify(arr, n, largest);
}

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

Ai

Blargest

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping wrong indices.

Not calling heapify recursively after swap.

We swap arr[i] with arr[largest] and then call heapify on largest to fix the subtree.