Queue

Queue is a linear data structure that follows the First In First Out (FIFO) principle. Elements are added at the rear (enqueue) and removed from the front (dequeue).

Circular Queue

A circular queue is a linear data structure that follows the FIFO principle but connects the end of the queue back to the front, forming a circle. This allows for efficient use of space by reusing empty slots created by dequeued elements.

public class CircularQueue {
  private String[] items;
  private int n = 0;
  private int head = 0;
  private int tail = 0;
 
  public CircularQueue(int capacity) {
    items = new String[capacity];
    n = capacity;
  }
 
  public boolean enqueue(String item) {
    if ((tail + 1) % n == head) return false;
    items[tail] = item;
    tail = (tail + 1) % n;
    return true;
  }
 
  public String dequeue() {
    if (head == tail) return null;
    String ret = items[head];
    head = (head + 1) % n;
    return ret;
  }
}