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CodeEasy v0.1

Design Circular Queue

Medium Subject: Design
Time Complexity
O(1)
Space Complexity
O(K)

Problem Description

Problem Statement

Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO principle, and the last position is connected back to the first position to make a circle. Implement MyCircularQueue with enQueue, deQueue, Front, Rear, isEmpty, isFull.

Example 1:

  • Input: ["MyCircularQueue", "enQueue", "enQueue", "enQueue", "enQueue", "Rear", "isFull", "deQueue", "enQueue", "Rear"]\n[[3], [1], [2], [3], [4], [], [], [], [4], []]
  • Output: [null, true, true, true, false, 3, true, true, true, 4]

Optimal Solution

Python

Approach: Array with Front and Rear Pointers

Use an array of fixed size k. Maintain front (points to the first element) and rear (points to the last element). Use modulo arithmetic index % k to wrap the pointers around the array boundaries.

class MyCircularQueue:
    def __init__(self, k: int):
        self.q = [0] * k
        self.k = k
        self.front = 0
        self.rear = -1
        self.size = 0

    def enQueue(self, value: int) -> bool:
        if self.isFull(): return False
        self.rear = (self.rear + 1) % self.k
        self.q[self.rear] = value
        self.size += 1
        return True

    def deQueue(self) -> bool:
        if self.isEmpty(): return False
        self.front = (self.front + 1) % self.k
        self.size -= 1
        return True

    def Front(self) -> int:
        return -1 if self.isEmpty() else self.q[self.front]

    def Rear(self) -> int:
        return -1 if self.isEmpty() else self.q[self.rear]

    def isEmpty(self) -> bool:
        return self.size == 0

    def isFull(self) -> bool:
        return self.size == self.k