【Java】数据结构-循环队列
本帖最后由 孤樱懶契 于 2021-10-23 22:36 编辑# 队列 Queue
> - ## 队列是一种先进先出的数据结果
# 循环队列实现输出截图
!(https://gitee.com/gylq/cloudimages/raw/master/img/image-20210625210003170.png)
# 循环队列实现代码（完整）
Queue.java（队列接口）
```java
public interface Queue<E> {
int getSize();
boolean isEmpty();
void enqueue(E e);
E dequeue();
E getFront();
}
```
LoopQueue.java
```java
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;
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 = 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;
data = 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;
}
private void resize(int newCapacity){
E[] newData =(E[]) new Object;
for(int i = 0 ; i < size ; i ++)
newData = data[(i + front) % data.length];
data = newData;
front = 0;
tail = size;
}
@Override
public String toString(){
StringBuilder res = new StringBuilder();
res.append(String.format("LoopQueue: size = %d, capacity = %d \n", size, getCapacity()));
res.append("front [");
for(int i = front ; i != tail; i = (i + 1) % data.length) {
res.append(data);
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<>();
for (int i = 0; i < 10; i++) {
queue.enqueue(i);
System.out.println(queue);
if (i % 3 == 2) {
queue.dequeue();
System.out.println(queue);
}
}
}
}
``` 收藏了再说 有注释就更好了
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