public class MyCircularQueue {
private int[] arr;
private int capacity;
/**
* front 指向当前队列中最早入队的元素
*/
private int front;
/**
* rear 指向下一个添加到队尾的元素
*/
private int rear;
/**
* Initialize your data structure here. Set the size of the queue to be k.
*/
public MyCircularQueue(int k) {
// 始终保持 1 个位置不存有效元素，是为了避免判断队列为空和队列为满的条件冲突
capacity = k + 1;
arr = new int[capacity];
front = 0;
rear = 0;
}
/**
* Insert an element into the circular queue. Return true if the operation is successful.
*/
public boolean enQueue(int value) {
// 队尾为满不可以入队
if (isFull()) {
return false;
}
arr[rear] = value;
rear = (rear + 1) % capacity;
return true;
}
/**
* Delete an element from the circular queue. Return true if the operation is successful.
*/
public boolean deQueue() {
// 队尾为空不可以出队
if (isEmpty()) {
return false;
}
front = (front + 1) % capacity;
return true;
}
/**
* Get the front item from the queue.
*/
public int Front() {
// 队列非空才可以取出队头
if (isEmpty()) {
return -1;
}
return arr[front];
}
/**
* Get the last item from the queue.
*/
public int Rear() {
// 队列非空才可以取出队尾
if (isEmpty()) {
return -1;
}
// 有数组下标的计算一定要考虑是否越界
return arr[(rear - 1 + capacity) % capacity];
}
/**
* Checks whether the circular queue is empty or not.
*/
public boolean isEmpty() {
return front == rear;
}
/**
* Checks whether the circular queue is full or not.
*/
public boolean isFull() {
// 有数组下标的计算一定要考虑是否越界
return (rear + 1) % capacity == front;
}
}
