622. Design Circular Queue.java

package leetcode.Queue;

class MyCircularQueue {
    final int[] a;
    // 这里 front 的初始值是0！！！
    // 数组为空时 front = rear + 1
    int front, rear = -1, len = 0;

    public MyCircularQueue(int k) { a = new int[k];}

    public boolean enQueue(int val) {
        if (!isFull()) {
            rear = (rear + 1) % a.length;
            a[rear] = val;
            len++;
            return true;
        } else return false;
    }

    public boolean deQueue() {
        if (!isEmpty()) {
            front = (front + 1) % a.length;
            len--;
            return true;
        } else return false;
    }

    public int Front() { return isEmpty() ? -1 : a[front];}

    public int Rear() {return isEmpty() ? -1 : a[rear];}

    public boolean isEmpty() { return len == 0;}

    public boolean isFull() { return len == a.length;}

}