Queue实现
2024-10-19 14:44:37
1.Queue接口：
public interface Queue<E> {
int getSize();
boolean isEmpty();
void enqueue(E e);
E dequeue();
E getFront();
}
2.使用Array数组实现ArrayQueue:
public class ArrayQueue<E> implements Queue<E> {
private Array<E> array;
public ArrayQueue(int capacity){
array = new Array<>(capacity);
}
public ArrayQueue(){
array = new Array<>();
}
@Override
public int getSize(){
return array.getSize();
}
@Override
public boolean isEmpty(){
return array.isEmpty();
}
public int getCapacity(){
return array.getCapacity();
}
@Override
public void enqueue(E e){
array.addLast(e);
}
@Override
public E dequeue(){
return array.removeFirst();
}
@Override
public E getFront(){
return array.getFirst();
}
@Override
public String toString(){
StringBuilder res = new StringBuilder();
res.append("Queue: ");
res.append("front [");
for(int i = 0 ; i < array.getSize() ; i ++){
res.append(array.get(i));
if(i != array.getSize() - 1)
res.append(", ");
}
res.append("] tail");
return res.toString();
}
public static void main(String[] args){
ArrayQueue<Integer> queue = new ArrayQueue<>();
for(int i = 0 ; i < 10 ; i ++){
queue.enqueue(i);
System.out.println(queue);
if(i % 3 == 2){
queue.dequeue();
System.out.println(queue);
}
}
}
}
3.使用LinkedList链表实现LinkedListQueue：
public class LinkedListQueue<E> implements Queue<E> {
private class Node{
public E e;
public Node next;
public Node(E e, Node next){
this.e = e;
this.next = next;
}
public Node(E e){
this(e, null);
}
public Node(){
this(null, null);
}
@Override
public String toString(){
return e.toString();
}
}
private Node head, tail;
private int size;
public LinkedListQueue(){
head = null;
tail = null;
size = 0;
}
@Override
public int getSize(){
return size;
}
@Override
public boolean isEmpty(){
return size == 0;
}
@Override
public void enqueue(E e){
if(tail == null){
tail = new Node(e);
head = tail;
}
else{
tail.next = new Node(e);
tail = tail.next;
}
size ++;
}
@Override
public E dequeue(){
if(isEmpty())
throw new IllegalArgumentException("Cannot dequeue from an empty queue.");
Node retNode = head;
head = head.next;
retNode.next = null;
if(head == null)
tail = null;
size --;
return retNode.e;
}
@Override
public E getFront(){
if(isEmpty())
throw new IllegalArgumentException("Queue is empty.");
return head.e;
}
@Override
public String toString(){
StringBuilder res = new StringBuilder();
res.append("Queue: front ");
Node cur = head;
while(cur != null) {
res.append(cur + "->");
cur = cur.next;
}
res.append("NULL tail");
return res.toString();
}
public static void main(String[] args){
LinkedListQueue<Integer> queue = new LinkedListQueue<>();
for(int i = 1 ; i < 11 ; i ++){
queue.enqueue(i);
System.out.println(queue);
if(i % 3 == 0){
queue.dequeue();
System.out.println(queue);
}
}
}
}
4.实现循环队列LoopQueue:
public class LoopQueue<E> implements Queue<E> {
private E[] data;
private int front, tail;
private int size;
public LoopQueue(int capacity){
data = (E[])new Object[capacity + 1];
front = 0;
tail = 0;
size = 0;
}
public LoopQueue(){
this(10);
}
public int getCapacity(){
return data.length - 1;
}
@Override
public boolean isEmpty(){
return front == tail;
}
@Override
public int getSize(){
return size;
}
@Override
public void enqueue(E e){
if((tail + 1) % data.length == front)
resize(getCapacity() * 2);
data[tail] = e;
tail = (tail + 1) % data.length;
size ++;
}
@Override
public E dequeue(){
if(isEmpty())
throw new IllegalArgumentException("Cannot dequeue from an empty queue.");
E ret = data[front];
data[front] = null;
front = (front + 1) % data.length;
size --;
if(size == getCapacity() / 4 && getCapacity() / 2 != 0)
resize(getCapacity() / 2);
return ret;
}
@Override
public E getFront(){
if(isEmpty())
throw new IllegalArgumentException("Queue is empty.");
return data[front];
}
private void resize(int newCapacity){
E[] newData = (E[])new Object[newCapacity + 1];
for(int i = 0 ; i < size ; i ++)
newData[i] = data[(i + front) % data.length];
data = newData;
front = 0;
tail = size;
}
@Override
public String toString(){
StringBuilder res = new StringBuilder();
res.append(String.format("Queue: size = %d , capacity = %d\n", size, getCapacity()));
res.append("front [");
for(int i = front ; i != tail ; i = (i + 1) % data.length){
res.append(data[i]);
if((i + 1) % data.length != tail)
res.append(", ");
}
res.append("] tail");
return res.toString();
}
public static void main(String[] args){
LoopQueue<Integer> queue = new LoopQueue<>(5);
for(int i = 0 ; i < 10 ; i ++){
queue.enqueue(i);
System.out.println(queue);
if(i % 3 == 2){
queue.dequeue();
System.out.println(queue);
}
}
}
}
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