Heap Sort Algorithm in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to swap two elements in the slice.

DSA Go

func swap(arr []int, i, j int) {
    temp := arr[[1]]
    arr[i] = arr[j]
    arr[j] = temp
}

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Ai

Bj

C0

Dlen(arr)-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong index like j or 0 for temp storage.

Forgetting to store the value before overwriting.

The swap function uses the index i to temporarily store the value before swapping.

2fill in blank

medium

Complete the code to find the left child index in the heap.

DSA Go

func leftChild(i int) int {
    return 2*[1] + 1
}

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A1

B2

Ci

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using a fixed number instead of the variable i.

Adding 2 instead of 1.

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

3fill in blank

hard

Fix the error in the heapify function to correctly compare parent and child nodes.

DSA Go

func heapify(arr []int, n, i int) {
    largest := i
    l := 2*i + 1
    r := 2*i + 2

    if l < n && arr[l] [1] arr[largest] {
        largest = l
    }

    if r < n && arr[r] > arr[largest] {
        largest = r
    }

    if largest != i {
        swap(arr, i, largest)
        heapify(arr, n, largest)
    }
}

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A!=

B==

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which breaks max-heap property.

Using '==' or '!=' which are incorrect for comparison.

To maintain max-heap property, we check if child is greater than parent.

4fill in blank

hard

Fill both blanks to build the max heap from the array.

DSA Go

func buildMaxHeap(arr []int, n int) {
    for i := n/[1] - 1; i >= 0; i-- {
        heapify(arr, n, [2])
    }
}

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A2

Bi

C1

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Using n or 1 instead of 2 for division.

Passing wrong index to heapify.

We start heapify from the last parent node at n/2 -1 down to 0.

5fill in blank

hard

Fill all three blanks to complete the heap sort main loop.

DSA Go

func heapSort(arr []int) {
    n := len(arr)
    buildMaxHeap(arr, n)

    for i := n - 1; i > 0; i-- {
        swap(arr, 0, [1])
        heapify(arr, [2], [3])
    }
}

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Ai

C0

Dn - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong indices for swap or heapify.

Not reducing heap size correctly.

Swap root with last element i, then heapify with reduced size i and root index 0.