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Stack And Queue Interview Questions and Answers

1
Describe stack operation.

Stack is a data structure that follows Last in First out strategy.

Stack Operations:-

  • Push – Pushes (inserts) the element in the stack. The location is specified by the pointer.
  • Pop – Pulls (removes) the element out of the stack. The location is specified by the pointer
  • Swap: - the two top most elements of the stack can be swapped
  • Peek: - Returns the top element on the stack but does not remove it from the stack
  • Rotate:- the topmost (n) items can be moved on the stack in a rotating fashion

A stack has a fixed location in the memory. When a data element is pushed in the stack, the pointer points to the current element.

2
Can you explain queue operation?

Queue is a data structure that follows First in First out strategy.

Queue Operations:

Push – Inserts the element in the queue at the end.
Pop – removes the element out of the queue from the front
Size – Returns the size of the queue
Front – Returns the first element of the queue.
Empty – to find if the queue is empty.

3
Discuss how to implement queue using stack.

A queue can be implemented by using 2 stacks:-

  1. An element is inserted in the queue by pushing it into stack 1
  2. An element is extracted from the queue by popping it from the stack 2
  3. If the stack 2 is empty then all elements currently in stack 1 are transferred to stack 2 but in the reverse order
  4. If the stack 2 is not empty just pop the value from stack 2.
4
Explain stacks and queues in detail?

A stack is a data structure based on the principle Last In First Out. Stack is container to hold nodes and has two operations - push and pop. Push operation is to add nodes into the stack and pop operation is to delete nodes from the stack and returns the top most node.

A queue is a data structure based on the principle First in First Out. The nodes are kept in an order. A node is inserted from the rear of the queue and a node is deleted from the front. The first element inserted in the first element first to delete.

5
What are priority queues?

A priority queue is essentially a list of items in which each item has associated with it a priority
Items are inserted into a priority queue in any, arbitrary order. However, items are withdrawn from a priority queue in order of their priorities starting with the highest priority item first.

Priority queues are often used in the implementation of algorithms

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