Array Deletion at Middle Index in DSA C# - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the element at the middle index from the array.

DSA C#

int[] arr = {1, 2, 3, 4, 5};
int mid = arr.Length / 2;
int[] result = new int[arr.Length - 1];
for (int i = 0, j = 0; i < arr.Length; i++) {
    if (i == [1]) continue;
    result[j++] = arr[i];
}

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

A0

Barr.Length

Cmid

Darr.Length / 2 + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong index to skip, like 0 or arr.Length.

Not skipping any index, causing no deletion.

The middle index is stored in 'mid', so we skip copying the element at index 'mid' to delete it.

2fill in blank

medium

Complete the code to print all elements of the array after deletion.

DSA C#

foreach (int num in [1]) {
    Console.Write(num + " ");
}

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

Aresult

Barr

Cnew int[0]

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the original array instead of the updated one.

Using null or empty arrays causing no output.

After deletion, the new array 'result' holds the updated elements to print.

3fill in blank

hard

Fix the error in the loop condition to avoid out-of-range errors.

DSA C#

for (int i = 0; i < [1]; i++) {
    Console.Write(result[i] + " ");
}

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

Aarr.Length

Bresult.Length + 1

Carr.Length - 1

Dresult.Length

Attempts:

3 left

💡 Hint

Common Mistakes

Using the original array length causing index out of range.

Using incorrect length values causing runtime errors.

The loop should run up to the length of 'result', the new array after deletion.

4fill in blank

hard

Fill both blanks to correctly shift elements after deletion.

DSA C#

for (int i = [1]; i < arr.Length - 1; i++) {
    arr[i] = arr[[2]];
}

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

Amid

Bi + 1

Ci - 1

Dmid + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Starting from wrong index causing incorrect shifts.

Using wrong index for assignment causing data loss.

Start shifting from the middle index, assigning each element the next element's value.

5fill in blank

hard

Fill all three blanks to create a new array after shifting elements.

DSA C#

int[] newArr = new int[arr.Length - 1];
for (int i = 0; i < [1]; i++) {
    newArr[i] = arr[i];
}
for (int i = [2]; i < newArr.Length; i++) {
    newArr[i] = arr[[3]];
}

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

Amid

Ci + 1

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Incorrect loop ranges causing index errors.

Wrong source index causing wrong elements copied.

Copy elements before middle index, then copy elements after middle index shifted by one.

Practice

1. What happens when you delete the middle element from an array in C#?

easy

A. The element is removed and all elements after it shift left by one position.

B. The array size automatically decreases by one without shifting elements.

C. The middle element is replaced by zero but array size stays the same.

D. The array throws an error because arrays have fixed size.

Solution

1. Step 1: Understand array behavior on deletion

   In C#, arrays have fixed size, so to delete an element, we shift elements after it left to overwrite it.

2. Step 2: Effect on array elements

   After shifting, the last element is duplicated or ignored logically, but the middle element is effectively removed from the sequence.

3. Final Answer:

   The element is removed and all elements after it shift left by one position. -> Option A

4. Quick Check:

   Deletion shifts elements left [OK]

Hint: Deleting means shifting elements left to fill the gap [OK]

Common Mistakes:

• Thinking array size changes automatically
• Assuming deletion replaces element with zero
• Believing arrays throw error on deletion

2. Which of the following C# code snippets correctly deletes the middle element from an integer array arr of odd length?

easy

A. int mid = arr.Length / 2; arr[mid] = 0;

B. int mid = arr.Length / 2; for(int i = mid; i < arr.Length - 1; i++) arr[i] = arr[i + 1];

C. int mid = arr.Length / 2; arr.RemoveAt(mid);

D. int mid = arr.Length / 2; Array.Delete(arr, mid);

Solution

1. Step 1: Identify valid deletion method in arrays

   Arrays in C# do not have RemoveAt or Delete methods; we must shift elements manually.

2. Step 2: Check code correctness

   int mid = arr.Length / 2; for(int i = mid; i < arr.Length - 1; i++) arr[i] = arr[i + 1]; calculates middle index and shifts elements left from middle to end-1, correctly deleting the middle element.

3. Final Answer:

   int mid = arr.Length / 2; for(int i = mid; i < arr.Length - 1; i++) arr[i] = arr[i + 1]; -> Option B

4. Quick Check:

   Manual shift after mid index [OK]

Hint: Use loop to shift elements left from middle index [OK]

Common Mistakes:

• Using non-existent array methods like RemoveAt
• Just setting middle element to zero without shifting
• Trying to delete without shifting elements

3. What is the output of the following C# code?

int[] arr = {10, 20, 30, 40, 50};
int mid = arr.Length / 2;
for(int i = mid; i < arr.Length - 1; i++)
    arr[i] = arr[i + 1];
for(int i = 0; i < arr.Length - 1; i++)
    Console.Write(arr[i] + " ");

medium

A. 10 20 30 50

B. 10 20 30 40 50

C. 10 20 40 50

D. 10 20 40 50 50

Solution

1. Step 1: Calculate middle index and shift elements

   Array length is 5, mid = 2. Loop shifts arr[2] = arr[3] (40), arr[3] = arr[4] (50).

2. Step 2: Print elements except last

   Loop prints arr[0]=10, arr[1]=20, arr[2]=40, arr[3]=50. Last element ignored.

3. Final Answer:

   10 20 40 50 -> Option C

4. Quick Check:

   Shifted middle element out = 10 20 40 50 [OK]

Hint: Shift elements left, print all but last [OK]

Common Mistakes:

• Printing full array including last duplicate
• Not shifting elements correctly
• Confusing middle index calculation

4. Find the error in this code that tries to delete the middle element from an array arr of length 6:

int mid = arr.Length / 2;
for(int i = mid; i <= arr.Length - 1; i++)
    arr[i] = arr[i + 1];

medium

A. Array elements are not shifted correctly.

B. Middle index calculation is wrong for even length arrays.

C. No error; code works fine.

D. Loop condition causes index out of range error.

Solution

1. Step 1: Analyze loop range and array indexing

   Loop runs from mid to arr.Length - 1 inclusive, accessing arr[i + 1]. For i = arr.Length - 1, arr[i + 1] is out of bounds.

2. Step 2: Identify cause of error

   Accessing arr[arr.Length] causes IndexOutOfRangeException.

3. Final Answer:

   Loop condition causes index out of range error. -> Option D

4. Quick Check:

   Loop index out of bounds [OK]

Hint: Loop must stop before last index to avoid out of range [OK]

Common Mistakes:

• Using <= instead of < in loop condition
• Ignoring array bounds when accessing i+1
• Misunderstanding middle index for even length

5. You have an array arr = {5, 10, 15, 20, 25, 30, 35}. Write the steps to delete the middle element and print the resulting array with correct size handling.

hard

A. Create a list from arr; remove element at mid; convert back to array; print.

B. Calculate mid = arr.Length / 2; shift elements left from mid; print first arr.Length - 1 elements.

C. Use Array.RemoveAt(mid); print arr.

D. Set arr[mid] = 0; print arr as is.

Solution

1. Step 1: Convert array to list for flexible size

   Arrays have fixed size, so convert to List<int> to remove element easily.

2. Step 2: Remove middle element and convert back

   Remove element at mid index, then convert list back to array for printing.

3. Step 3: Print resulting array

   Print elements of new array which has one less element.

4. Final Answer:

   Create a list from arr; remove element at mid; convert back to array; print. -> Option A

5. Quick Check:

   Use List for deletion, then convert back [OK]

Hint: Use List to delete middle element easily, then convert back [OK]

Common Mistakes:

• Trying to resize arrays directly
• Only shifting elements without resizing
• Using non-existent Array.RemoveAt method