public class QueueB {
static class Queue {
static int arr[];
static int size;
static int rear;
static int front;
Queue(int n) {
arr = new int[n];
size = n;
rear = -1;
front = -1;
}
public boolean isEmpty() {
return rear == -1 && front == -1;
}
public boolean isFull() {
return (rear + 1) % size == front;
}
// add
public void add(int data) {
if (isFull()) {
System.out.println("Queue is full");
return;
}
// add 1st element
if (front == -1) {
front = 0;
}
rear = (rear + 1) % size;
arr[rear] = data;
}
// remove
public int remove() {
if (isEmpty()) {
System.out.println("Queue is empty");
return -1;
}
int result = arr[front];
// last element deleted
if (rear == front) {
rear = front = -1;
} else {
front = (front + 1) % size;
}
return result;
}
// peek
public int peek() {
if (isEmpty()) {
System.out.println("Queue is empty");
return -1;
}
return arr[front];
}
}
public static void main(String args[]) {
Queue q = new Queue(3);
q.add(1);
q.add(2);
q.add(3);
// adding condition that works like a circular queue
System.out.println(q.remove()); // prints 1
q.add(4);
System.out.println(q.remove()); // prints 2
q.add(5);
// queue now contains 3,4,5 in order
while (!q.isEmpty()) {
System.out.println(q.peek());
q.remove();
}
}
}
OUTPUT:
1
2
3
4
5
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