CycleQueue
CycleQueue.java 源码
package datastructure.queue;
import java.util.Arrays;
/**
* @author roseduan[roseduan520@gmail.com]
* @time 2019/10/31 23:31
* @description 循环队列简单实现
*/
public class CycleQueue<T> {
private static final int DEFAULT_SIZE = 16;
private Object[] data;
private int capacity;
private int size;
private int head;
private int tail;
public CycleQueue(int capacity) {
this.data = new Object[capacity];
this.capacity = capacity;
this.size = 0;
this.head = 0;
this.tail = 0;
}
public CycleQueue(){
this(DEFAULT_SIZE);
}
/**
* 入队列
*/
public boolean add(T value) {
//队列满，需要扩容
if ((tail + 1) % capacity == head) {
resize(data, capacity + (capacity >> 1));
}
data[tail] = value;
tail = (tail + 1) % capacity;
size++;
return true;
}
/**
* 出队列
*/
@SuppressWarnings("unchecked")
public T dequeue(){
if (head == tail){
return null;
}
T result = (T) data[head];
data[head] = null;
head = (head + 1) % capacity;
size--;
if (size < (capacity >> 1)){
resize(data, (capacity >> 1));
head = 0;
tail = size - 1;
}
return result;
}
@Override
public String toString() {
return Arrays.toString(data);
}
/**
* 扩容和缩容
*/
private void resize(Object[] data, int newCapacity){
Object[] temp = new Object[newCapacity];
int k = 0;
while (head != tail){
temp[k++] = data[head];
head = (head + 1) % capacity;
}
this.data = temp;
this.capacity = newCapacity;
}
}
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