CareerCup

Just create your own singly linked list w/ the appropriate (FIFO) pointer?

we can use Doubly or singly Linked List

keep a tail pointer and a head pointer

public class Queue<T> {
    private static class Node {
        Node previous;
        Node next;
        T value;
        
        public Node(T value, Node next, Node previous) {
            this.value = value;
            this.next = next;
            this.previous = previous;
        }
    }

    private head = null;
    private tail = null;
    private int size = 0;
    private int maxSize = 0;
    public Queue(int size) {
        this.maxSize = size;
    }
    
    public void insert(T value) {
        if (head == null) {
            head = new Node(value, null, null);
            tail = head;
            size += 1;
        } else {
            if (this.size == this.maxSize) {
                throw new Exception("Queue is full");
            }
            Node tempNode = new Node(value, head, null);
            head.previous = tempNode;
            head = tempNode;
            size += 1;
        }
    }
    
    public T pop() {
        if (this.size < 1) {
            throw new Exception("Queue is empty");
        } else if (size == 1) {
            T value = head.value;
            head = null;
            tail = null;
            size = 0;
            return value;
        }
        Node tempNode = tail;
        tail.previous.next = null;
        tail = tempNode.previous;
        size -= 1;
        return tempNode.value;
    }
}

import java.util.Queue;


...


done