package pointer;

/**

* @Author: wei1

* @Date: Create in 2018/11/17 21:34

* @Description: 用数组模拟一个队列，通过size来控制有没有满的逻辑很重要

*/

public class ArrayQueue {

private Integer[] arr;

private Integer size;

private Integer first;

private Integer last;

public ArrayQueue(int initSize) {

if (initSize < 0) {

throw new IllegalArgumentException("The init size is less than 0");

}

arr = new Integer[initSize];

size = 0;

first = 0;

last = 0;

}

// 要求实现三个方法

public void push(Integer value) {

if (size.equals(arr.length)) {

throw new IllegalArgumentException("The stack_queue is full");

}

//注意index指向最后一个数前一个

if (last == arr.length - 1) {

arr[last] = value;

last = 0;

} else {

arr[last++] = value;

}

size++;

}

public Integer poll() {

if (size == 0) {

throw new ArrayIndexOutOfBoundsException("The queue is empty");

}

if (first == arr.length - 1) {

int result = arr[first];

first = 0;

size--;

return result;

} else {

size--;

return arr[first++];

}

}

public Integer peek() {

if (size == 0) {

return null;

}

return arr[first];

}

public static void main(String[] args) {

ArrayStack arrayStack = new ArrayStack(2);

arrayStack.push(1);

arrayStack.push(2);

// arrayStack.push(1);

System.out.println(arrayStack.peek());

System.out.println(arrayStack.poll());

System.out.println(arrayStack.poll());

// System.out.println(arrayStack.poll());

}

}