Array Deletion at Middle Index in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the middle element from the list.

DSA Python

arr = [1, 2, 3, 4, 5]
mid = len(arr) // 2
arr.[1](mid)
print(arr)

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

Ainsert

Bremove

Cappend

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() which removes by value, not index.

Using append() or insert() which add elements instead of removing.

The pop method removes an element at a specific index. Here, mid is the middle index.

2fill in blank

medium

Complete the code to find the middle index of the list correctly.

DSA Python

arr = [10, 20, 30, 40, 50, 60]
mid = [1]
print(mid)

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

Alen(arr) / 2

Blen(arr) // 2

Clen(arr) - 1

Dlen(arr) + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using / which returns a float, causing errors when used as index.

Using len(arr) - 1 which gives last index, not middle.

Using integer division // gives the middle index as an integer.

3fill in blank

hard

Fix the error in the code to delete the middle element from the list.

DSA Python

arr = [7, 8, 9, 10, 11]
mid = len(arr) // 2
arr.[1](mid)
print(arr)

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

Ainsert

Bremove

Cpop

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() with an index value instead of the element value.

Using append() or insert() which add elements instead of removing.

The code incorrectly uses remove with an index value. pop should be used with index to remove by position.

4fill in blank

hard

Fill both blanks to create a new list without the middle element.

DSA Python

arr = [2, 4, 6, 8, 10]
mid = len(arr) // 2
new_arr = [arr[[1]] for [2] in range(len(arr)) if [2] != mid]
print(new_arr)

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

Ai

Bj

Cx

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing NameError.

Using the middle index inside the list comprehension causing wrong output.

Use the same variable i for indexing and iteration to skip the middle index.

5fill in blank

hard

Fill all three blanks to delete the middle element and print the updated list.

DSA Python

arr = [3, 5, 7, 9, 11, 13]
mid = len(arr) // 2
arr.[1](mid)
print(arr[[2]:[3]])

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

Apop

B0

Cmid

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() instead of pop() causing errors.

Incorrect slice indices causing wrong output.

Use pop to remove the middle element by index. Then print the list slice from start to middle index.

Practice

1. What happens when you delete the middle element from an array with an odd number of elements?

easy

A. The element at the exact middle index is removed, and the array size decreases by one.

B. The first element is removed instead of the middle one.

C. The array size remains the same but the middle element is set to zero.

D. The last element is removed instead of the middle one.

Solution

1. Step 1: Identify the middle index in an odd-length array

   For an array with odd length n, the middle index is n//2 (integer division).

2. Step 2: Remove the element at the middle index

   Deleting the element at this index reduces the array size by one and shifts elements after it left.

3. Final Answer:

   The element at the exact middle index is removed, and the array size decreases by one. -> Option A

4. Quick Check:

   Middle element removed = The element at the exact middle index is removed, and the array size decreases by one. [OK]

Hint: Middle index = length // 2 for odd arrays [OK]

Common Mistakes:

• Removing first or last element instead of middle
• Not reducing array size after deletion
• Confusing middle index calculation

2. Which of the following Python statements correctly deletes the middle element from a list named arr with odd length?

easy

A. arr.pop(len(arr))

B. del arr[len(arr)//2]

C. arr.remove(len(arr)//2)

D. arr.delete(len(arr)//2)

Solution

1. Step 1: Understand Python deletion syntax

   The del statement removes an element at a specific index from a list.

2. Step 2: Calculate middle index and delete

   Using len(arr)//2 gives the middle index for odd length. So del arr[len(arr)//2] deletes the middle element correctly.

3. Final Answer:

   del arr[len(arr)//2] -> Option B

4. Quick Check:

   Correct syntax for deletion = del arr[len(arr)//2] [OK]

Hint: Use del with index: del arr[len(arr)//2] [OK]

Common Mistakes:

• Using remove() which deletes by value, not index
• Using pop() with wrong index
• Using non-existent delete() method

3. What is the output of the following code?

arr = [10, 20, 30, 40, 50]
del arr[len(arr)//2]
print(arr)

medium

A. [10, 30, 40, 50]

B. [10, 20, 30, 40]

C. [20, 30, 40, 50]

D. [10, 20, 40, 50]

Solution

1. Step 1: Calculate middle index

   Length of arr is 5, so middle index = 5 // 2 = 2.

2. Step 2: Delete element at index 2 and print

   Element at index 2 is 30. After deletion, arr becomes [10, 20, 40, 50].

3. Final Answer:

   [10, 20, 40, 50] -> Option D

4. Quick Check:

   Deleted arr[2] = 30, remaining = [10, 20, 40, 50] [OK]

Hint: Middle index 2 in 5 elements; delete arr[2] [OK]

Common Mistakes:

• Deleting wrong index (like 3 or 1)
• Confusing element value with index
• Printing before deletion

4. The following code is intended to delete the middle element from an array arr. What is the error?

arr = [1, 2, 3, 4, 5]
arr.remove(len(arr)//2)
print(arr)

medium

A. It deletes the last element instead of the middle one.

B. It causes an IndexError because remove expects an index.

C. It deletes the element with value 2 instead of the middle index element.

D. There is no error; it deletes the middle element correctly.

Solution

1. Step 1: Understand remove() method behavior

   remove(x) deletes the first element with value x, not at index x.

2. Step 2: Analyze the argument passed to remove()

   len(arr)//2 = 5//2 = 2, so arr.remove(2) deletes element with value 2, not element at index 2.

3. Final Answer:

   It deletes the element with value 2 instead of the middle index element. -> Option C

4. Quick Check:

   remove deletes by value, not index = It deletes the element with value 2 instead of the middle index element. [OK]

Hint: remove() deletes by value, del deletes by index [OK]

Common Mistakes:

• Confusing remove() with del or pop()
• Expecting remove() to delete by index
• Not calculating middle index correctly

5. Given an array arr = [5, 10, 15, 20, 25, 30] with even length, which code correctly deletes the middle element(s) so that after deletion the array is [5, 10, 25, 30]?

hard

A. del arr[len(arr)//2 - 1]; del arr[len(arr)//2]

B. del arr[len(arr)//2]; del arr[len(arr)//2 - 1]

C. arr.pop(len(arr)//2); arr.pop(len(arr)//2 - 1)

D. arr.remove(len(arr)//2); arr.remove(len(arr)//2 - 1)

Solution

1. Step 1: Identify middle indices for even length array

   Length is 6, middle indices are 2 and 3 (0-based), values 15 and 20.

2. Step 2: Delete elements at indices 2 and 3 accounting for length change

   del arr[len(arr)//2 - 1] deletes index 2 (15), array becomes [5, 10, 20, 25, 30]. Then del arr[len(arr)//2] deletes new index 2 (20), resulting in [5, 10, 25, 30].

3. Final Answer:

   del arr[len(arr)//2 - 1]; del arr[len(arr)//2] -> Option A

4. Quick Check:

   del arr[2] then del arr[2] (after shift) = [5, 10, 25, 30] [OK]

Hint: For even length, delete lower middle index first then the new middle index [OK]

Common Mistakes:

• Deleting higher index first without adjusting for length change
• Using pop() in wrong order causing incorrect shifts
• Using remove() which deletes by value