Array Deletion at Beginning in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output after deleting first element from array

What will be the output of the following C code after deleting the first element from the array?

DSA C

int arr[] = {10, 20, 30, 40, 50};
int n = 5;

// Delete first element by shifting
for (int i = 0; i < n - 1; i++) {
    arr[i] = arr[i + 1];
}
n--;

for (int i = 0; i < n; i++) {
    printf("%d ", arr[i]);
}

A 50 40 30 20

B 10 20 30 40 50

C 30 40 50

D 20 30 40 50

💡 Hint

After deleting the first element, all elements shift left by one position.

The code shifts all elements left by one, overwriting the first element. The size reduces by one, so the output prints elements from index 0 to n-1, which are 20, 30, 40, 50.

❓ Predict Output

intermediate

Resulting array size after deletion

Given an array of size 7, after deleting the first element by shifting, what is the new size of the array?

DSA C

int arr[7] = {5, 10, 15, 20, 25, 30, 35};
int n = 7;

// Delete first element
for (int i = 0; i < n - 1; i++) {
    arr[i] = arr[i + 1];
}
n--;

A 7

B 6

C 5

D 0

💡 Hint

Deleting one element reduces the size by one.

The size variable n is decremented by one after deletion, so new size is 6.

🔧 Debug

advanced

Identify the bug in array deletion code

What is the bug in the following code that deletes the first element of an array?

DSA C

int arr[] = {1, 2, 3, 4, 5};
int n = 5;

for (int i = 0; i <= n - 1; i++) {
    arr[i] = arr[i + 1];
}
n--;

for (int i = 0; i < n; i++) {
    printf("%d ", arr[i]);
}

A Loop condition should be i < n - 1, not i <= n - 1

B n should be incremented, not decremented

C Array size is not initialized

D No bug, code works correctly

💡 Hint

Check the loop boundary to avoid accessing out of bounds.

The loop runs one step too far, accessing arr[n] which is out of bounds. It should run till i < n - 1 to avoid this.

❓ Predict Output

advanced

Output after multiple deletions at beginning

What is the output after deleting the first element twice from the array?

DSA C

int arr[] = {100, 200, 300, 400, 500};
int n = 5;

// Delete first element twice
for (int d = 0; d < 2; d++) {
    for (int i = 0; i < n - 1; i++) {
        arr[i] = arr[i + 1];
    }
    n--;
}

for (int i = 0; i < n; i++) {
    printf("%d ", arr[i]);
}

A 100 200 300 400 500

B 200 300 400 500

C 300 400 500

D 400 500

💡 Hint

Each deletion shifts elements left and reduces size by one.

After first deletion, array is 200,300,400,500; after second deletion, 300,400,500 remain.

🧠 Conceptual

expert

Time complexity of deleting first element in array

What is the time complexity of deleting the first element from an array of size n by shifting all elements left by one?

A O(n)

B O(1)

C O(n^2)

D O(log n)

💡 Hint

Consider how many elements need to be moved.

Deleting the first element requires shifting all remaining n-1 elements left, so time complexity is linear O(n).