Array Deletion at End in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output after deleting the last element?

Consider the following Python code that deletes the last element from an array. What will be printed?

DSA Python

arr = [10, 20, 30, 40, 50]
arr.pop()
print(arr)

A [10, 20, 30, 40]

B [10, 20, 30, 40, 50]

C [20, 30, 40, 50]

D []

💡 Hint

The pop() method removes the last element from the list.

The pop() method removes the last element (50) from the list, so the remaining list is [10, 20, 30, 40].

❓ Predict Output

intermediate

What happens if we delete the last element from an empty array?

What error will this code produce?

DSA Python

arr = []
arr.pop()
print(arr)

A []

B IndexError: pop from empty list

C None

D TypeError: pop() missing required argument

💡 Hint

You cannot pop from an empty list.

Calling pop() on an empty list raises an IndexError because there is no element to remove.

🔧 Debug

advanced

Why does this code raise an error when deleting the last element?

Find the reason for the error in this code snippet.

DSA Python

arr = [1, 2, 3]
arr.pop(3)
print(arr)

A SyntaxError due to wrong pop syntax

B TypeError because pop() takes no arguments

C IndexError because index 3 is out of range

D No error, output is [1, 2]

💡 Hint

pop(index) removes element at given index; index must be valid.

The list has indices 0,1,2. pop(3) tries to remove element at index 3 which does not exist, causing IndexError.

🧠 Conceptual

advanced

What is the time complexity of deleting the last element from an array?

Consider a dynamic array (like Python list). What is the time complexity of deleting the last element?

A O(1) constant time

B O(n) linear time

C O(log n) logarithmic time

D O(n^2) quadratic time

💡 Hint

Deleting the last element does not require shifting other elements.

Deleting the last element is done in constant time because no elements need to be moved.

❓ Predict Output

expert

What is the final array after multiple deletions at the end?

What will be printed after these operations?

DSA Python

arr = [5, 10, 15, 20, 25]
arr.pop()
arr.pop()
arr.pop()
print(arr)

A [10, 15, 20]

B [5, 10, 15, 20]

C [5, 10, 15]

D [5, 10]

💡 Hint

Each pop() removes one element from the end.

Three pop() calls remove 25, 20, and 15, leaving [5, 10].

Practice

1. What happens when you delete the last element from an array in Python using pop()?

easy

A. The first element is removed and the array size stays the same.

B. The last element is removed and the array size decreases by one.

C. The array is cleared completely.

D. The array becomes empty but elements remain.

Solution

1. Step 1: Understand the pop() method

   The pop() method removes the last element from the array (list) by default.

2. Step 2: Effect on array size

   After removal, the array size decreases by one because one element is deleted.

3. Final Answer:

   The last element is removed and the array size decreases by one. -> Option B

4. Quick Check:

   pop() removes last element [OK]

Hint: pop() removes last item and shrinks array [OK]

Common Mistakes:

• Thinking pop() removes the first element
• Assuming pop() clears the whole array
• Believing array size stays the same after pop()

2. Which of the following is the correct syntax to delete the last element from a list named arr in Python?

easy

A. arr.pop()

B. arr.delete()

C. pop(arr)

D. arr.remove_last()

Solution

1. Step 1: Identify the correct method for deletion at end

   In Python, pop() is the method used to remove the last element from a list.

2. Step 2: Check syntax correctness

   The correct syntax is arr.pop(). Other options are invalid or do not exist in Python.

3. Final Answer:

   arr.pop() -> Option A

4. Quick Check:

   pop() is correct syntax [OK]

Hint: Use arr.pop() to remove last element [OK]

Common Mistakes:

• Using arr.delete() which is invalid
• Trying pop(arr) instead of arr.pop()
• Using arr.remove_last() which does not exist

3. What is the output of the following code?

arr = [10, 20, 30, 40]
arr.pop()
print(arr)

medium

A. [10, 20, 30]

B. [20, 30, 40]

C. [10, 20, 30, 40]

D. [10, 20, 40]

Solution

1. Step 1: Understand pop() effect on arr

   The pop() removes the last element, which is 40.

2. Step 2: Print the updated array

   After removal, the array becomes [10, 20, 30].

3. Final Answer:

   [10, 20, 30] -> Option A

4. Quick Check:

   Last element removed, array shrinks [OK]

Hint: pop() removes last element, print updated list [OK]

Common Mistakes:

• Expecting original array unchanged
• Removing first element instead of last
• Confusing pop() with remove()

4. Find the error in the following code that tries to delete the last element from arr:

arr = [1, 2, 3]
arr.pop(0)
print(arr)

medium

A. pop() deletes the entire array

B. pop() cannot take any arguments

C. pop() should be replaced with remove()

D. pop(0) removes the first element, not the last

Solution

1. Step 1: Analyze pop(0) usage

   pop(0) removes the element at index 0, which is the first element, not the last.

2. Step 2: Identify correct method to delete last element

   To delete the last element, pop() should be called without arguments.

3. Final Answer:

   pop(0) removes the first element, not the last -> Option D

4. Quick Check:

   pop(index) removes element at index [OK]

Hint: pop() without argument removes last element [OK]

Common Mistakes:

• Assuming pop() cannot take arguments
• Using pop(0) to remove last element
• Confusing pop() with remove()

5. Given the list arr = [5, 10, 15, 20, 25], you want to remove the last two elements using pop(). Which code snippet correctly achieves this?

hard

A. arr.pop(1)
arr.pop(0)

B. arr.pop(3)
arr.pop(2)

C. arr.pop()
arr.pop()

D. arr.pop(0)
arr.pop(1)

Solution

1. Step 1: Understand pop() without argument

   Calling pop() without arguments removes the last element each time.

2. Step 2: Apply pop() twice to remove last two elements

   Calling arr.pop() twice removes 25 then 20, the last two elements.

3. Step 3: Check other options

   Options A, B, and C use indices that become invalid or remove wrong elements after first pop.

4. Final Answer:

   arr.pop() followed by arr.pop() -> Option C

5. Quick Check:

   pop() twice removes last two elements [OK]

Hint: Use pop() twice to remove last two elements [OK]

Common Mistakes:

• Using pop() with fixed indices without updating
• Removing first elements instead of last
• Assuming pop() clears multiple elements at once