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Design a circular queue data structure | Optiver Coding Question

Quick Overview

This question evaluates understanding of circular buffer data structures and the ability to implement fixed-capacity queue operations with O(1) time and O(k) space guarantees, testing skills in index management and state representation within the Coding & Algorithms domain.

Design a circular queue data structure

Company: Optiver

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

## Problem Design and implement a fixed-capacity **circular queue** that supports constant-time operations. A circular queue stores elements in an array of size `k` and uses wrap-around indices so that freed space at the front can be reused. ### API to implement Create a class (or module) with the following methods: - `MyCircularQueue(k)`: initialize the queue with capacity `k`. - `enQueue(x) -> bool`: insert element `x` into the queue. Return `true` if the operation succeeds; return `false` if the queue is full. - `deQueue() -> bool`: delete the element from the front of the queue. Return `true` if the operation succeeds; return `false` if the queue is empty. - `Front() -> int`: get the front element. Return `-1` if the queue is empty. - `Rear() -> int`: get the last element. Return `-1` if the queue is empty. - `isEmpty() -> bool`: return whether the queue is empty. - `isFull() -> bool`: return whether the queue is full. ### Constraints / requirements - `1 <= k <= 10^5` - Each operation should run in **O(1)** time. - Use **O(k)** additional space. ### Notes Be careful to correctly handle wrap-around behavior and the distinction between **empty** and **full** states.

Quick Answer: This question evaluates understanding of circular buffer data structures and the ability to implement fixed-capacity queue operations with O(1) time and O(k) space guarantees, testing skills in index management and state representation within the Coding & Algorithms domain.

Implement a fixed-capacity circular queue (ring buffer) that supports standard queue operations efficiently. You are given the queue capacity `k` and a list of operations to perform in order. Each operation is one of: - ('enq', x): enqueue integer x. Return True if successful, otherwise False (queue full). - ('deq',): dequeue the front element. Return True if successful, otherwise False (queue empty). - ('front',): return the front element, or -1 if empty. - ('rear',): return the last (most recently enqueued) element, or -1 if empty. - ('isEmpty',): return True if the queue is empty, else False. - ('isFull',): return True if the queue is full, else False. Return a list containing the outputs of every operation, in the same order as the operations are given.

Constraints

1 <= k <= 100000
1 <= len(operations) <= 200000
For ('enq', x), x is an integer in the 32-bit signed range
operations contain only: 'enq', 'deq', 'front', 'rear', 'isEmpty', 'isFull'

Examples

Input: (3, [('enq', 1), ('enq', 2), ('enq', 3), ('enq', 4), ('rear',), ('isFull',), ('deq',), ('enq', 4), ('rear',), ('front',)])

Expected Output: [True, True, True, False, 3, True, True, True, 4, 2]

Explanation: Queue fills to capacity 3; enq(4) fails. After one deq, enq(4) succeeds and wraps around.

Input: (1, [('deq',), ('front',), ('enq', 5), ('isFull',), ('enq', 6), ('rear',), ('deq',), ('isEmpty',)])

Expected Output: [False, -1, True, True, False, 5, True, True]

Explanation: Capacity 1: cannot dequeue or read front when empty; cannot enqueue when full.

Quick Overview