Animal Shelter Queue LeetCode (Animal Shelter Simulation Using Queue)

 Construct animal queue that consists of the following features:

1. Contains Cats and Dogs
2. If not preference on animal type is needed, then fetch the animal that was placed first in the queue
3. If Cat is needed then fetch the Cat that was added first
4. If Dog is needed then fetch the Dog that was added first

This is an interesting real-world use of Queue data structure and is well discussed in several coding and algorithm books, including Cracking the coding Interview, and several other coding forums - Page1 A collection of hundreds of interview questions and solutions are available in our blog at Interview Question

Solution

	import java.util.LinkedList;
	class Animal {
	String name;
	int order;
	public Animal(String n) {
	name = n;
	}
	public void setName(String n) {
	name = n;
	}
	public String getName() {
	return name;
	}
	public void setOrder(int o) {
	order = o;
	}
	public int getOrder() {
	return order;
	}
	public String toString() {
	return name + "," + order;
	}
	}
	class Dog extends Animal {
	public Dog(String a) {
	super(a);
	}
	}
	class Cat extends Animal {
	public Cat(String a) {
	super(a);
	}
	}
	public class AnimalQueue {
	LinkedList<Cat> cats = new LinkedList<Cat>();
	LinkedList<Dog> dogs = new LinkedList<Dog>();
	int order = 0;
	public void enqueue(Animal a) {
	a.setOrder(order++);
	if (a instanceof Dog) {
	//add to dog queue
	dogs.add((Dog)a);
	} else {
	cats.add((Cat)a);
	}
	}
	public Cat dequeueCat() throws Exception {
	if (cats.isEmpty()) {
	throw new Exception("Cat queue is empty");
	}
	return cats.removeFirst();
	}
	public Dog dequeueDog() throws Exception {
	if (dogs.isEmpty()) {
	throw new Exception("Dog queue is empty");
	}
	return dogs.removeFirst();
	}
	public Animal dequeueAny() throws Exception {
	//get the animal with smallest id
	if (cats.isEmpty() && dogs.isEmpty()) {
	throw new Exception("animal queue is empty");
	} else if (cats.isEmpty()) {
	return dogs.removeFirst();
	} else if (dogs.isEmpty()) {
	return cats.removeFirst();
	} else {
	return cats.peek().getOrder() < dogs.peek().getOrder() ? cats.removeFirst() : dogs.removeFirst();
	}
	}
	public static void main(String args[]) throws Exception {
	Cat c1 = new Cat("cat1");
	Cat c2 = new Cat("cat2");
	Cat c3 = new Cat("cat3");
	Dog d1 = new Dog("dog1");
	Dog d2 = new Dog("dog2");
	Dog d3 = new Dog("dog3");
	AnimalQueue animals = new AnimalQueue();
	animals.enqueue(c1);
	animals.enqueue(c2);
	animals.enqueue(d1);
	animals.enqueue(d2);
	animals.enqueue(c3);
	animals.enqueue(d3);
	//now lets dequeu the animals
	Animal a = animals.dequeueAny();
	System.out.println("dequeue any:" + a.toString());
	a = animals.dequeueCat();
	System.out.println("dequeue cat:" + a.toString());
	a = animals.dequeueCat();
	System.out.println("dequeue cat:" + a.toString());
	a = animals.dequeueAny();
	System.out.println("dequeue any:" + a.toString());
	a = animals.dequeueAny();
	System.out.println("dequeue any:" + a.toString());
	}
	}

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