Implement Stack using Queues · Interview Problem

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Leetcode

Medium

Stacks

Queues

Design

Implement Stack using Queues

Design a stack that supports standard stack operations using one or more queues.

Acceptance 100%

Start Practice

Problem Statement

Problem

Implement a last-in, first-out (LIFO) stack using only queue operations.

You need to support the usual stack interface:

push(x): add element x onto the stack
pop(): remove and return the top element
top(): return the top element without removing it
empty(): return whether the stack is empty

You may use one or more queues internally, but the exposed behavior must match a normal stack.

Notes

The order of removal must follow stack semantics, not queue semantics.
Assume the caller uses the operations in any valid order.
If the stack is empty, pop() and top() behavior is typically defined by the platform; for practice, you can assume they are called only when valid unless specified otherwise.

Input Format

A sequence of operations on a stack object.
push(x) receives one integer value.
pop(), top(), and empty() take no arguments.

Output Format

pop() returns the removed top element.
top() returns the current top element.
empty() returns true if the stack has no elements, otherwise false.

Constraints

Implement the stack using queue operations only.
Typical practice constraints are small to moderate, but the design should support repeated operations efficiently enough for interview use.
Element values are integers.

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