package org.huhuiyu.datastructures;

public class ArrayQueue {
	private int count;
	private int front; // 前端索引
	private int back; // 尾端索引
	private Object[] datas; // 隊列數據

	public ArrayQueue(int size) {
		datas = new Object[size];
		clear();
	}

	/**
	 * 加入數據到隊列
	 * 
	 * @param data
	 *            加入到隊列的數據
	 */
	public void enqueue(Object data) {
		if (count == datas.length) {
			throw new IllegalStateException("隊列已滿！");
		}
		back = (back + 1) % datas.length; // 計算隊列末端索引
		datas[back] = data; // 加入到隊列末端
		count++;
	}

	/**
	 * 出隊并返回出隊的數據
	 * 
	 * @return 出隊的數據
	 */
	public Object dequeue() {
		if (isEmpty()) {
			throw new IllegalStateException("隊列是空的！");
		}
		front = (front + 1) % datas.length; // 計算隊列前端索引
		Object data = datas[front]; // 獲取隊列前端數據
		datas[front] = null; // 置空數組數據
		count--;
		return data;
	}

	/**
	 * 查看排在隊列最前端的數據
	 * 
	 * @return 排在隊列最前端的數據
	 */
	public Object peek() {
		if (isEmpty()) {
			throw new IllegalStateException("隊列是空的！");
		}
		return datas[front];
	}

	public void clear() {
		front = 0;
		back = 0;
		count = 0;
	}

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

	public int size() {
		return count;
	}

	public static void main(String[] args) {
		int length = 10;
		ArrayQueue queue = new ArrayQueue(length);
		for (int i = 0; i < length; i++) {
			queue.enqueue(i);
		}
		System.out.println(queue.dequeue());
		System.out.println(queue.dequeue());
		queue.enqueue(10);
		System.out.println(queue.peek());
		while (!queue.isEmpty()) {
			System.out.println(queue.dequeue());
		}
	}
}