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

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output after deleting the first element?

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

DSA Python

arr = [10, 20, 30, 40, 50]
del arr[0]
print(arr)

A [20, 30, 40, 50]

B IndexError

C [30, 40, 50]

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

💡 Hint

Deleting the first element removes the element at index 0.

The del statement removes the element at index 0, so the array starts from the second element onward.

❓ Predict Output

intermediate

What is the output after popping the first element?

What will be the output of this code that removes the first element using pop?

DSA Python

arr = [5, 15, 25, 35]
removed = arr.pop(0)
print(arr)

A [5, 15, 25, 35]

B [15, 25, 35]

C [25, 35]

D IndexError

💡 Hint

pop(0) removes and returns the first element.

pop(0) removes the element at index 0, so the array starts from the second element.

🔧 Debug

advanced

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

Identify the error in this code and what error it raises.

DSA Python

arr = [1, 2, 3]
del arr[3]
print(arr)

A SyntaxError

B IndexError: list assignment index out of range

C IndexError: list deletion index out of range

D No error, prints [1, 2, 3]

💡 Hint

Index 3 does not exist in a list of length 3.

Deleting an element at an index outside the list length raises IndexError with message 'list deletion index out of range'.

❓ Predict Output

advanced

What is the output after removing the first element using slicing?

What will be printed after this slicing operation that removes the first element?

DSA Python

arr = [7, 14, 21, 28]
arr = arr[1:]
print(arr)

A [14, 21, 28]

B [7]

C [7, 14, 21, 28]

D TypeError

💡 Hint

Slicing from index 1 to end excludes the first element.

arr[1:] creates a new list starting from index 1 to the end, effectively removing the first element.

🧠 Conceptual

expert

What is the time complexity of deleting the first element in a Python list?

Consider a Python list with n elements. What is the time complexity of deleting the first element using del arr[0] or arr.pop(0)?

A O(1) - Constant time

B O(log n) - Logarithmic time

C O(n^2) - Quadratic time

D O(n) - Linear time

💡 Hint

Think about what happens to the rest of the elements after deletion.

Deleting the first element requires shifting all other elements one position left, which takes linear time O(n).