Shell Sort Algorithm in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the gap for Shell Sort.

DSA C++

int n = arr.size();
int gap = [1];

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

An * 2

Bn / 2

C1

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Using gap equal to the full array size causes no sorting.

Using gap larger than array size causes errors.

The initial gap in Shell Sort is usually set to half the array size to start sorting elements far apart.

2fill in blank

medium

Complete the code to reduce the gap in each iteration of Shell Sort.

DSA C++

while (gap > 0) {
    // sorting logic here
    gap = [1];
}

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

Agap - 1

Bgap + 1

Cgap / 2

Dgap * 2

Attempts:

3 left

💡 Hint

Common Mistakes

Subtracting 1 reduces gap too slowly.

Multiplying gap increases it, causing infinite loop.

Shell Sort reduces the gap by dividing it by 2 each iteration to gradually sort closer elements.

3fill in blank

hard

Fix the error in the inner loop condition to correctly compare elements during insertion sort step.

DSA C++

for (int i = gap; i < n; i++) {
    int temp = arr[i];
    int j = i;
    while (j >= gap && arr[j - gap] [1] temp) {
        arr[j] = arr[j - gap];
        j -= gap;
    }
    arr[j] = temp;
}

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

A>

B>=

C<

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' causes incorrect sorting order.

Using '>=' causes unnecessary shifts.

We move elements that are greater than temp to the right to insert temp in the correct position.

4fill in blank

hard

Fill both blanks to complete the insertion step inside the gap-based sorting.

DSA C++

int temp = arr[[1]];
int j = [2];
while (j >= gap && arr[j - gap] > temp) {
    arr[j] = arr[j - gap];
    j -= gap;
}

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

Ai

Bgap

Dj

Attempts:

3 left

💡 Hint

Common Mistakes

Using gap as index causes out-of-bound errors.

Using j before initialization causes errors.

We store the current element at index i in temp and start shifting from index j = i.

5fill in blank

hard

Fill all three blanks to complete the Shell Sort function.

DSA C++

void shellSort(std::vector<int>& arr) {
    int n = arr.size();
    for (int gap = [1]; gap > 0; gap = [2]) {
        for (int i = gap; i < n; i++) {
            int temp = arr[[3]];
            int j = i;
            while (j >= gap && arr[j - gap] > temp) {
                arr[j] = arr[j - gap];
                j -= gap;
            }
            arr[j] = temp;
        }
    }
}

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

An / 2

Bgap / 2

Ci

Dgap

Attempts:

3 left

💡 Hint

Common Mistakes

Using gap as index instead of i.

Increasing gap instead of decreasing causes infinite loop.

The Shell Sort starts with gap = n/2, reduces gap by half each iteration, and uses i as the current index for insertion.