Array Deletion at Middle Index in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output after deleting middle element from array

What is the output of the following C code after deleting the middle element from the array?

DSA C

#include <stdio.h>

void deleteMiddle(int arr[], int *n) {
    int mid = *n / 2;
    for (int i = mid; i < *n - 1; i++) {
        arr[i] = arr[i + 1];
    }
    (*n)--;
}

int main() {
    int arr[] = {10, 20, 30, 40, 50};
    int n = 5;
    deleteMiddle(arr, &n);
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    return 0;
}

A 10 20 30 50

B 10 20 40 50

C 20 30 40 50

D 10 20 30 40 50

💡 Hint

Remember that deleting the middle element means shifting elements after the middle one to the left.

The middle index for an array of size 5 is 2 (0-based). The element at index 2 (30) is removed, and elements after it (40, 50) shift left. The new array is 10, 20, 40, 50.

❓ Predict Output

intermediate

Resulting array size after middle deletion

What is the size of the array after deleting the middle element using the code below?

DSA C

void deleteMiddle(int arr[], int *n) {
    int mid = *n / 2;
    for (int i = mid; i < *n - 1; i++) {
        arr[i] = arr[i + 1];
    }
    (*n)--;
}

int main() {
    int arr[] = {1, 2, 3, 4, 5, 6};
    int n = 6;
    deleteMiddle(arr, &n);
    printf("%d", n);
    return 0;
}

A 3

B 6

C 5

D 4

💡 Hint

Deleting one element reduces the size by one.

Initially, the array size is 6. After deleting the middle element (index 3), the size decreases by 1 to 5.

🔧 Debug

advanced

Identify the error in middle deletion code

What error will occur when running this code to delete the middle element?

DSA C

void deleteMiddle(int arr[], int *n) {
    int mid = (*n + 1) / 2;
    for (int i = mid; i < *n; i++) {
        arr[i] = arr[i + 1];
    }
    (*n)--;
}

int main() {
    int arr[] = {5, 10, 15, 20, 25};
    int n = 5;
    deleteMiddle(arr, &n);
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    return 0;
}

A Runtime error due to out-of-bounds access

B Runs correctly and outputs: 5 10 20 25

C Runs but outputs: 5 10 15 20 25

D Compilation error due to syntax

💡 Hint

Check the loop boundary and array indexing carefully.

The loop runs from mid to n, and accesses arr[i + 1]. When i = n - 1, arr[i + 1] accesses arr[n], which is out of bounds causing runtime error.

❓ Predict Output

advanced

Output after deleting middle element from even-sized array

What is the output of this code after deleting the middle element from an even-sized array?

DSA C

#include <stdio.h>

void deleteMiddle(int arr[], int *n) {
    int mid = (*n - 1) / 2;
    for (int i = mid; i < *n - 1; i++) {
        arr[i] = arr[i + 1];
    }
    (*n)--;
}

int main() {
    int arr[] = {2, 4, 6, 8, 10, 12};
    int n = 6;
    deleteMiddle(arr, &n);
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    return 0;
}

A 2 4 8 10 12

B 2 4 6 8 10 12

C 2 4 6 10 12

D 4 6 8 10 12

💡 Hint

For even length, middle is the lower middle index.

For n=6, mid = (6-1)/2 = 2. Element at index 2 (6) is deleted. Elements after index 2 shift left. Result: 2 4 8 10 12.

🧠 Conceptual

expert

Time complexity of deleting middle element in array

What is the time complexity of deleting the middle element from an array of size n by shifting elements?

A O(n^2) - Quadratic time

B O(log n) - Logarithmic time

C O(1) - Constant time

D O(n) - Linear time

💡 Hint

Consider how many elements need to be moved after deletion.

Deleting the middle element requires shifting roughly half the elements, which is proportional to n, so time complexity is O(n).