89. OCR A Level (H046-H446) SLR14 – 1.4 Data structures part 3 –

What data structure is known as a LIFO structure?

• Linked List

• Stack

• Queue

• Array

Answer explanation

A LIFO structure is known as a Stack, where the last element added is the first one to be removed. Stacks follow the Last In First Out principle.

What operation is used to add an item to the top of a stack?

• Pop

• Dequeue

• Push

• Enqueue

Answer explanation

To add an item to the top of a stack, the operation used is 'Push'.

What happens when you try to pop an item from an empty stack?

• Queue Underflow

• Queue Overflow

• Stack Underflow

• Stack Overflow

Answer explanation

Popping an item from an empty stack results in Stack Underflow, indicating that the stack is empty and no item can be removed.

Which of the following is NOT a use case for stacks?

• Process scheduling

• Performing depth-first searches

• Evaluating mathematical expressions

• Tracking the flow of programs

Answer explanation

Process scheduling is NOT a use case for stacks as it is typically handled by other scheduling algorithms like round-robin or priority-based scheduling.

What is the correct term for adding an item to a queue?

• Enqueuing

• Popping

• Pushing

• Peeking

Answer explanation

The correct term for adding an item to a queue is 'Enqueuing'. This operation involves inserting an element at the rear end of the queue.

Which data structure operates on a FIFO basis?

• Tree

• Array

• Stack

• Queue

Answer explanation

A Queue operates on a FIFO (First In, First Out) basis, where the first element added is the first to be removed. This makes Queue the correct choice for the given question.

What is a stack overflow?

• Adding an item to a full stack

• Removing an item from an empty stack

• Removing the bottom item of the stack

• Looking at the top item of the stack

Answer explanation

A stack overflow occurs when an item is added to a full stack, causing it to exceed its capacity and resulting in a memory error.

Which of the following is a potential problem when implementing a queue using an array?

• Running out of space

• Infinite looping

• Stack overflow

• Queue underflow

Answer explanation

When implementing a queue using an array, a potential problem is running out of space due to fixed array size, leading to the need for resizing or dynamic allocation.

What is the purpose of a stack pointer?

• To point to the first item in a queue

• To indicate the full capacity of a stack

• To indicate the bottom of a stack

• To point to the top item in a stack

Answer explanation

The purpose of a stack pointer is to point to the top item in a stack, allowing for easy access and manipulation of data in the stack.

What does 'peeking' allow you to do in a stack?

• Remove the top item

• Check if the stack is empty

• Add an item to the top

• Look at the top item without removing it

Answer explanation

Peeking allows you to look at the top item in a stack without removing it, making it a non-destructive operation.