数据结构之队列

队列是一种特殊的线性表,特殊之处在于它只允许在表的前端（front）进行删除操作，而在表的后端（rear）进行插入操作，和栈一样，队列是一种操作受限制的线性表。进行插入操作的端称为队尾，进行删除操作的端称为队头。先进先出（FIFO—first in first out）

队列分为普通队列和环形队列

这里说说环形队列

package song.queue;

/**
 * Created by sfz on 2017/8/25.
 */
public class MyQueue {

    private int[] data;

    //队列数组的长度
    private int size = 0;
    //对头的下标
    private int head = 0;
    //队尾的下标
    private int tail = 0;
    //队列实际 的个数
    private int queuelen = 0;

    //初始化队列
    public MyQueue(int size) {
        this.size = size;
        data = new int[size];
        clearQueue();
    }


    /**
     * 清空队列
     */
    public void clearQueue() {
        head = 0;
        tail = 0;
        queuelen = 0;
    }

    /**
     * 队列判空
     *
     * @return
     */
    public boolean isEmpty() {
        return queuelen == 0;
    }

    /**
     * 实际长度
     *
     * @return
     */
    public int queueLength() {
        return queuelen;
    }

    /**
     * 判满
     *
     * @return
     */
    public boolean isfull() {
        return queuelen == size;
    }

    /**
     * 入队
     *
     * @param ele
     * @return
     */
    public boolean enQueue(int ele) {
        if (isfull()) {
            return false;
        } else {
            data[tail] = ele;
            tail++;
            tail = tail % size;
            queuelen++;
            return true;
        }
    }


    /**
     * 出对
     *
     * @param ele
     * @return
     */
    public boolean deQqueue(int ele) {
        if (isEmpty()) {
            return false;
        } else {
            data[head] = 0;
            head++;
            head = head % size;
            queuelen--;
            return true;
        }


    }

    /**
     * 遍历
     */
    public void traverse() {
        for (int i = head; i < queuelen+head; i++) {
            int val = data[i % size];
            System.out.print(val+ " ");
        }
        System.out.println();
    }

}

package song.queue;

import org.junit.Test;
import song.tree.Tree;

/**
 * Created by sfz on 2017/8/25.
 */
public class Test001 {

    @Test
    public void test001() throws Exception {

        MyQueue myQueue = new MyQueue(4);

        myQueue.enQueue(10);
        myQueue.enQueue(20);
        myQueue.enQueue(30);
        myQueue.enQueue(40);

        myQueue.traverse();



        myQueue.deQqueue(0);
        myQueue.deQqueue(0);
        myQueue.traverse();




        myQueue.enQueue(50);
        myQueue.enQueue(60);
        myQueue.traverse();

        myQueue.clearQueue();
        myQueue.traverse();


        myQueue.enQueue(70);
        myQueue.enQueue(80);
        myQueue.traverse();



    }
}