Circular Queue Data Structure (2024)

Python

Java

C

C+

# Circular Queue implementation in Pythonclass MyCircularQueue(): def __init__(self, k): self.k = k self.queue = [None] * k self.head = self.tail = -1 # Insert an element into the circular queue def enqueue(self, data): if ((self.tail + 1) % self.k == self.head): print("The circular queue is full\n") elif (self.head == -1): self.head = 0 self.tail = 0 self.queue[self.tail] = data else: self.tail = (self.tail + 1) % self.k self.queue[self.tail] = data # Delete an element from the circular queue def dequeue(self): if (self.head == -1): print("The circular queue is empty\n") elif (self.head == self.tail): temp = self.queue[self.head] self.head = -1 self.tail = -1 return temp else: temp = self.queue[self.head] self.head = (self.head + 1) % self.k return temp def printCQueue(self): if(self.head == -1): print("No element in the circular queue") elif (self.tail >= self.head): for i in range(self.head, self.tail + 1): print(self.queue[i], end=" ") print() else: for i in range(self.head, self.k): print(self.queue[i], end=" ") for i in range(0, self.tail + 1): print(self.queue[i], end=" ") print()# Your MyCircularQueue object will be instantiated and called as such:obj = MyCircularQueue(5)obj.enqueue(1)obj.enqueue(2)obj.enqueue(3)obj.enqueue(4)obj.enqueue(5)print("Initial queue")obj.printCQueue()obj.dequeue()print("After removing an element from the queue")obj.printCQueue()

// Circular Queue implementation in Javapublic class CQueue { int SIZE = 5; // Size of Circular Queue int front, rear; int items[] = new int[SIZE]; CQueue() { front = -1; rear = -1; } // Check if the queue is full boolean isFull() { if (front == 0 && rear == SIZE - 1) { return true; } if (front == rear + 1) { return true; } return false; } // Check if the queue is empty boolean isEmpty() { if (front == -1) return true; else return false; } // Adding an element void enQueue(int element) { if (isFull()) { System.out.println("Queue is full"); } else { if (front == -1) front = 0; rear = (rear + 1) % SIZE; items[rear] = element; System.out.println("Inserted " + element); } } // Removing an element int deQueue() { int element; if (isEmpty()) { System.out.println("Queue is empty"); return (-1); } else { element = items[front]; if (front == rear) { front = -1; rear = -1; } /* Q has only one element, so we reset the queue after deleting it. */ else { front = (front + 1) % SIZE; } return (element); } } void display() { /* Function to display status of Circular Queue */ int i; if (isEmpty()) { System.out.println("Empty Queue"); } else { System.out.println("Front -> " + front); System.out.println("Items -> "); for (i = front; i != rear; i = (i + 1) % SIZE) System.out.print(items[i] + " "); System.out.println(items[i]); System.out.println("Rear -> " + rear); } } public static void main(String[] args) { CQueue q = new CQueue(); // Fails because front = -1 q.deQueue(); q.enQueue(1); q.enQueue(2); q.enQueue(3); q.enQueue(4); q.enQueue(5); // Fails to enqueue because front == 0 && rear == SIZE - 1 q.enQueue(6); q.display(); int elem = q.deQueue(); if (elem != -1) { System.out.println("Deleted Element is " + elem); } q.display(); q.enQueue(7); q.display(); // Fails to enqueue because front == rear + 1 q.enQueue(8); }}

// Circular Queue implementation in C#include <stdio.h>#define SIZE 5int items[SIZE];int front = -1, rear = -1;// Check if the queue is fullint isFull() { if ((front == rear + 1) || (front == 0 && rear == SIZE - 1)) return 1; return 0;}// Check if the queue is emptyint isEmpty() { if (front == -1) return 1; return 0;}// Adding an elementvoid enQueue(int element) { if (isFull()) printf("\n Queue is full!! \n"); else { if (front == -1) front = 0; rear = (rear + 1) % SIZE; items[rear] = element; printf("\n Inserted -> %d", element); }}// Removing an elementint deQueue() { int element; if (isEmpty()) { printf("\n Queue is empty !! \n"); return (-1); } else { element = items[front]; if (front == rear) { front = -1; rear = -1; } // Q has only one element, so we reset the // queue after dequeing it. ? else { front = (front + 1) % SIZE; } printf("\n Deleted element -> %d \n", element); return (element); }}// Display the queuevoid display() { int i; if (isEmpty()) printf(" \n Empty Queue\n"); else { printf("\n Front -> %d ", front); printf("\n Items -> "); for (i = front; i != rear; i = (i + 1) % SIZE) { printf("%d ", items[i]); } printf("%d ", items[i]); printf("\n Rear -> %d \n", rear); }}int main() { // Fails because front = -1 deQueue(); enQueue(1); enQueue(2); enQueue(3); enQueue(4); enQueue(5); // Fails to enqueue because front == 0 && rear == SIZE - 1 enQueue(6); display(); deQueue(); display(); enQueue(7); display(); // Fails to enqueue because front == rear + 1 enQueue(8); return 0;}

// Circular Queue implementation in C++#include <iostream>#define SIZE 5 /* Size of Circular Queue */using namespace std;class Queue { private: int items[SIZE], front, rear; public: Queue() { front = -1; rear = -1; } // Check if the queue is full bool isFull() { if (front == 0 && rear == SIZE - 1) { return true; } if (front == rear + 1) { return true; } return false; } // Check if the queue is empty bool isEmpty() { if (front == -1) return true; else return false; } // Adding an element void enQueue(int element) { if (isFull()) { cout << "Queue is full"; } else { if (front == -1) front = 0; rear = (rear + 1) % SIZE; items[rear] = element; cout << endl << "Inserted " << element << endl; } } // Removing an element int deQueue() { int element; if (isEmpty()) { cout << "Queue is empty" << endl; return (-1); } else { element = items[front]; if (front == rear) { front = -1; rear = -1; } // Q has only one element, // so we reset the queue after deleting it. else { front = (front + 1) % SIZE; } return (element); } } void display() { // Function to display status of Circular Queue int i; if (isEmpty()) { cout << endl << "Empty Queue" << endl; } else { cout << "Front -> " << front; cout << endl << "Items -> "; for (i = front; i != rear; i = (i + 1) % SIZE) cout << items[i]; cout << items[i]; cout << endl << "Rear -> " << rear; } }};int main() { Queue q; // Fails because front = -1 q.deQueue(); q.enQueue(1); q.enQueue(2); q.enQueue(3); q.enQueue(4); q.enQueue(5); // Fails to enqueue because front == 0 && rear == SIZE - 1 q.enQueue(6); q.display(); int elem = q.deQueue(); if (elem != -1) cout << endl << "Deleted Element is " << elem; q.display(); q.enQueue(7); q.display(); // Fails to enqueue because front == rear + 1 q.enQueue(8); return 0;}