leetcode622.设计循环队列

题目链接

题解：

在我的文章数据结构之——队列与循环队列 中，有关于循环队列的设计，包括本题没有考虑过的resize操作。
对于本题而言，我们利用数组data作为循环队列的底层实现，并且维护了两个指针front和tail分别指向队列的头元素和尾部元素。除此之外我们刻意浪费了一个位置：

front == tail

而队列为满的条件是：

front == (tail+1)%data.length

搞清楚思路后，就可以写代码了，代码如下：

class MyCircularQueue {
    private int[] data;
    private int front;
    private int tail;



    /** Initialize your data structure here. Set the size of the queue to be k. */
    public MyCircularQueue(int k) {
        data = new int[k + 1];
        front = 0;
        tail = 0;
    }

    private int getSize(){
        if(tail < front){
            return data.length - front + tail;
        }else{
            return tail - front;
        }
    }
    
    /** Insert an element into the circular queue. Return true if the operation is successful. */
    public boolean enQueue(int value) {
        if(getSize() == data.length - 1){
            return false;
        }else{
            data[tail] = value;
            tail = (tail + 1)%data.length;
            return true;
        }   
    }
    
    /** Delete an element from the circular queue. Return true if the operation is successful. */
    public boolean deQueue() {
        if(getSize() == 0){
            return false;
        }else{
            front = (front + 1) % data.length;
            return true;
        }
    }
    
    /** Get the front item from the queue. */
    public int Front() {
        if(isEmpty()){
            return -1;
        }
        return data[front];
    }
    
    /** Get the last item from the queue. */
    public int Rear() {
        if(isEmpty()){
            return -1;
        }
        return data[(front + getSize() - 1) % data.length];
    }
    
    /** Checks whether the circular queue is empty or not. */
    public boolean isEmpty() {
        return front == tail;
    }
    
    /** Checks whether the circular queue is full or not. */
    public boolean isFull() {
        return getSize() == data.length - 1;
    }
}

/**
 * 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();
 */

执行结果: