LC.P622[设计循环队列]

方法一：双指针

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class MyCircularQueue {

    int[] data;
    int size, head, tail;

    public MyCircularQueue(int k) {
        data = new int[k];
        size = 0;
        head = 0;
        tail = k - 1;
    }
    
    public boolean enQueue(int value) {
        if (isFull()) return false;
        tail = tail == data.length - 1 ? 0 : tail + 1;
        data[tail] = value;
        ++size;
        return true;
    }
    
    public boolean deQueue() {
        if (isEmpty()) return false;
        head = head == data.length - 1 ? 0 : head + 1;
        --size;
        return true;
    }
    
    public int Front() {
        return isEmpty() ? -1 : data[head];
    }
    
    public int Rear() {
        return isEmpty() ? -1 : data[tail];
    }
    
    public boolean isEmpty() {
        return size == 0;
    }
    
    public boolean isFull() {
        return size == data.length;
    }
}

/**
 * Your MyCircularQueue object will be instantiated and called as such:
 * MyCircularQueue obj = new MyCircularQueue(k);
 * boolean param_1 = obj.enQueue(value);
 * boolean param_2 = obj.deQueue();
 * int param_3 = obj.Front();
 * int param_4 = obj.Rear();
 * boolean param_5 = obj.isEmpty();
 * boolean param_6 = obj.isFull();
 */

方法二：空闲单元法

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class MyCircularQueue {

    int[] data;
    int front;
    int rear;
    int size;

    public MyCircularQueue(int k) {
        size = k + 1;
        data = new int[size];
        front = rear = 0;
    }
    
    public boolean enQueue(int value) {
        if (isFull()) return false;
        data[rear] = value;
        rear = (rear + 1) % size;
        return true;
    }
    
    public boolean deQueue() {
        if (isEmpty()) return false;
        front = (front + 1) % size;
        return true;
    }
    
    public int Front() {
        return isEmpty() ? -1 : data[front];
    }
    
    public int Rear() {
        return isEmpty() ? -1 : data[(rear - 1 + size) % size];
    }
    
    public boolean isEmpty() {
        return front == rear;
    }
    
    public boolean isFull() {
        return front == (rear + 1) % size;
    }
}

/**
 * Your MyCircularQueue object will be instantiated and called as such:
 * MyCircularQueue obj = new MyCircularQueue(k);
 * boolean param_1 = obj.enQueue(value);
 * boolean param_2 = obj.deQueue();
 * int param_3 = obj.Front();
 * int param_4 = obj.Rear();
 * boolean param_5 = obj.isEmpty();
 * boolean param_6 = obj.isFull();
 */