扑克洗牌程序

随机数的使用

在java中可以使用 Random工具类生成随机数；
我们利用比较、交换的思想（排序算法经常用到）实现简易的扑克洗牌动作。

首先存在有序分扑克牌52张，我们用一个数组保存，洗牌时：

• 遍历扑克数组
• 生成随机数，得到需要交换的目标数组索引下标（注意，使用Random.nextInt(N),N需要小于数组的长度）
• 当前遍历到的元素与随机到的元素交换

完整的程序如下：

package org.byron4j.dsaa.basic;

import java.util.Random;

/**
 * 洗牌
 * @author BYRON.Y.Y
 *
 */
public class ShuffleCard {
	
	public static void main(String[] args) {
		
		String[] arr = {"2♣", "3♣", "4♣", "5♣", "6♣", "7♣", "8♣", "9♣", "10♣", "J♣", "Q♣", "K♣", "A♣", "2♦", "3♦", "4♦", "5♦", "6♦", "7♦", "8♦", "9♦", "10♦", "J♦","Q♦", "K♦", "A♦", "2♥", "3♥", "4♥", "5♥", "6♥", "7♥", "8♥", "9♥", "10♥", "J♥", "Q♥", "K♥", "A♥", "2♠", "3♠", "4♠", "5♠", "6♠", "7♠", "8♠", "9♠", "10♠", "J♠", "Q♠", "K♠", "A♠"};
		printf(arr, 13);
		shuffle(arr);
		System.out.println("\n***********************洗牌完毕*******************");
		
		printf(arr, 13);
	}
	
	public static void shuffle( Object[] arr ) {
		
		int n = arr.length;
		for( int i = 0; i < n ; i++ ) {
			int idx = new Random().nextInt(n);
			//交换
			Object tmp = arr[i];
			arr[i] = arr[idx];
			arr[idx] = tmp;
		}
		
	}
	
	/**
	 * 
	 * @param arr  数组
	 * @param nop  多少一行打印，默认为0表示一行打印出来
	 */
	public static void printf(Object[] arr, int nop) {
		if( nop <= 0 ) {
			for( int i = 0; i < arr.length; i++ ) {
				System.out.print((arr[i] + "  ").substring(0, 4));
			}
		}else {
			for( int i = 0; i < arr.length; i++ ) {
				System.out.print((arr[i] + "  ").substring(0, 4));
				if( ( i + 1 ) % nop == 0 ) System.out.println();
			}
		}
	}
	
}

程序运行结果如下：

2♣  3♣  4♣  5♣  6♣  7♣  8♣  9♣  10♣ J♣  Q♣  K♣  A♣  
2♦  3♦  4♦  5♦  6♦  7♦  8♦  9♦  10♦ J♦  Q♦  K♦  A♦  
2♥  3♥  4♥  5♥  6♥  7♥  8♥  9♥  10♥ J♥  Q♥  K♥  A♥  
2♠  3♠  4♠  5♠  6♠  7♠  8♠  9♠  10♠ J♠  Q♠  K♠  A♠  

***********************洗牌完毕*******************
3♥  K♠  8♦  2♥  Q♦  2♣  5♥  7♣  8♣  A♦  7♦  9♣  2♠  
10♦ J♥  K♣  7♥  10♠ A♣  4♥  K♦  A♥  A♠  4♦  7♠  J♦  
Q♣  4♣  9♥  3♣  2♦  6♠  6♦  3♠  Q♥  3♦  5♠  K♥  5♦  
6♥  9♠  5♣  6♣  10♣ Q♠  10♥ 4♠  8♠  J♣  9♦  8♥  J♠