泛型桥牌发牌应用--随机队列

算法第四版习题1.3.35~1.3.36

编写一个随机队列RandomQueue类来实现以下API：

RandomQueue() 创建一条空的随机队列

boolean isEmpty() 队列是否为空

void enqueue(Item item) 添加一个元素

Item dequeue() 删除并随机返回一个元素（取样且不放回）

Item sample() 随机返回一个元素但不删除它（取样且放回）

删除一个元素时，随机交换某个元素（索引在0和N-1之间）和末位元素（索引为N-1），然后删除并返回末位元素。编写一个桥牌用例。

另为上面的类编写一个迭代器，随机返回队列中的所有元素。

 

随机队列类：

package com.lch.Chapter1_3;

import edu.princeton.cs.algs4.StdOut;
import edu.princeton.cs.algs4.StdRandom;

/**
 * 
 * @author Lucas.Li
 *
 * @param <Item>
 */
public class RandomQueue<Item> {

    private int N;
    private Item[] array;

    @SuppressWarnings("unchecked")
    /**
     * 初始化数组array,大小为1
     */
    public RandomQueue() {
        array = (Item[]) new Object[1];
    }

    /**
     * 
     * @return 队列是否为空
     */
    public boolean isEmpty() {
        return N == 0;
    }

    /**
     * 
     * @return 队列大小
     */
    public int size() {
        return N;
    }

    @SuppressWarnings("unchecked")
    /**
     * 调整数组大小
     * @param max
     */
    public void resize(int max) {
        Item[] temp = (Item[]) new Object[max];
        for (int i = 0; i < N; i++) {
            temp[i] = array[i];
        }
        array = temp;
    }

    /**
     * 为队列添加元素
     * @param item
     */
    public void enqueue(Item item) {
        if (N == array.length) {
            resize(N * 2);
        }
        array[N++] = item;
    }

    /**
     * 
     * @return 随机交换后的末位元素
     */
    public Item dequeue() {
        if (N == 0) {
            try {
                throw new Exception("There is none in array.");
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return null;
        }
        if (N == (array.length / 4)) {
            resize(array.length / 2);
        }
        if (N == 1) {
            Item item = array[0];
            array[0] = null;
            return item;
        } else {
            int randomIndex = StdRandom.uniform(0, N - 1);
            Item temp = array[randomIndex];
            array[randomIndex] = array[N - 1];
            array[N - 1] = null;
            N--;
            return temp;
        }

    }

    /**
     * 
     * @return 随机元素
     */
    public Item sample() {
        Item item = array[StdRandom.uniform(N)];
        return item;
    }

    @SuppressWarnings("unchecked")
    /**
     * 迭代器：随机返回所有元素
     */
    public void randomIterator() {
        int M = N;
        Item[] temp = array;
        Item[] store = (Item[]) new Object[M];
        int m = 0;
        while (M > 1) {
            int random = StdRandom.uniform(M);
            Item tmp = temp[random];
            temp[random] = temp[M - 1];
            store[m] = tmp;
            M--;
            m++;
        }
        store[m] = temp[0];
        for (int i = 0; i < store.length; i++) {
            StdOut.print(store[i] + " ");
            if ((i + 1) % 13 == 0) {
                StdOut.println();
            }
        }
    }

    /**
     * 迭代器：按索引返回所有元素
     */
    public void iterator() {
        for (int i = 0; i < N; i++) {
            StdOut.print(array[i] + " ");
        }
        StdOut.println();
    }

}

 

桥牌方法：

/**
     * 
     * @param 牌面
     */
    public static void showCards(String[] cards) {
        for (int i = 0; i < cards.length; i++) {
            StdOut.print(cards[i] + " ");
        }
        StdOut.println();
    }

    /**
     * 
     * @return 52张牌
     */
    public static String[] playingCards() {
        String[] cards = new String[52];
        for (int i = 1; i < 10; i++) {
            cards[i * 4 - 4] = "heart" + (i + 1);
            cards[i * 4 - 3] = "spade" + (i + 1);
            cards[i * 4 - 2] = "club" + (i + 1);
            cards[i * 4 - 1] = "diamond" + (i + 1);
        }
        cards[36] = "heartJ";
        cards[37] = "spadeJ";
        cards[38] = "clubJ";
        cards[39] = "diamondJ";
        cards[40] = "heartQ";
        cards[41] = "spadeQ";
        cards[42] = "clubQ";
        cards[43] = "diamondQ";
        cards[44] = "heartK";
        cards[45] = "spadeK";
        cards[46] = "clubK";
        cards[47] = "diamondK";
        cards[48] = "heartA";
        cards[49] = "spadeA";
        cards[50] = "clubA";
        cards[51] = "diamondA";
        return cards;
    }

测试方法：

/**
     * 桥牌发牌
     */
    public static void p035() {
        String[] cards = playingCards();
        String[] player1 = new String[13];
        String[] player2 = new String[13];
        String[] player3 = new String[13];
        String[] player4 = new String[13];
        RandomQueue<String> randomQueue = new RandomQueue<String>();
        for (int i = 0; i < cards.length; i++) {
            randomQueue.enqueue(cards[i]);
        }
        for (int i = 0; i < 13; i++) {
            player1[i] = randomQueue.dequeue();
            player2[i] = randomQueue.dequeue();
            player3[i] = randomQueue.dequeue();
            player4[i] = randomQueue.dequeue();
        }
        StdOut.print("Player1's cards : ");
        showCards(player1);
        StdOut.print("Player2's cards : ");
        showCards(player2);
        StdOut.print("Player3's cards : ");
        showCards(player3);
        StdOut.print("Player4's cards : ");
        showCards(player4);
    }