我需要将一副牌分成两个包:上半部分和下半部分.这种新的卡阵列被假设去:第一卡从顶部包,从底部包,从顶部包,从底部包等第二卡第二卡第一卡如果有奇数个的卡然后顶部包应该比底部数据包多一个.甲板的顶部是阵列的前部.
我该怎么做呢？
这是我创建的用于生成卡片组的方法(我认为它有效):
private Card[] cards;
int value, suit;
private final int DECK_SIZE = 52;
public Deck()
{
int index = 0;
cards = new Card[DECK_SIZE];
//0 = spades, 1 = hearts, 2 = clovers, 3 =diamonds
int suits[] = {0, 1, 2, 3};
//1 = Ace, 11=jack, 12=queen, 13=king
int values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
for (int suit : suits)
for (int value : values)
{
cards[index] = new Card(value, suit);
index++;
}
}
你去这样做,你说什么之前,请注意一个完美的洗牌是不是,如果你正在寻找一个随机甲板的顺序是一个好主意:
一个完美的faro shuffle,卡片完美交替,被认为是最困难的卡片操作之一,因为它需要洗牌器将牌组切成两个相等的堆叠并在将半甲板推入每个牌组时施加恰当的压力其他.如果一个人设法连续执行八个完美的faro out-shuffle,那么52张牌的牌组将恢复到原来的顺序.如果一个人可以进行完美的洗牌,那么26次洗牌将颠倒牌组的顺序,另外26次将使其恢复到原始顺序.
另一方面,如果你想要一个随机的洗牌,那么走的路就是Fisher-Yates shuffle.从维基百科页面:
To shuffle an array a of n elements (indexes 0..n-1):
for i from n ? 1 downto 1 do
j ? random integer with 0 ? j ? i
exchange a[j] and a[i]
但请注意,根据您的随机性标准,标准Java随机数生成器可能还不够:(也来自维基百科页面:)
例如,由许多编程语言和/或库提供的内置伪随机数发生器通常可能只有32位的内部状态,这意味着它只能产生2 32个不同的数字序列.如果使用这样的发电机来洗牌一副52张扑克牌,它只会产生52张牌中的一小部分!≈2个225.6可能的排列.内部状态小于226位的发生器不可能产生52张牌的所有可能的排列.有人建议[需要引证]只有使用超过250比特状态的发生器才能确保洗牌是无偏的.
Mersenne Twister是一个众所周知的随机数发生器,足够了.
编辑:对于原始问题的字面答案,这是我可能会这样做(包括测试方法):
import java.util.Arrays;
public class Shuffle {
/* assumes input and output arrays are same length (N) */
static public <T> void perfectShuffle(T[] input, T[] output, int N)
{
int itop = 0;
int ibottom = N - (N/2);
/* bottom has (N/2) elements; for odd N this is rounded down,
* and the top part has 1 more element */
int k = 0;
while (ibottom < N)
{
output[k++] = input[itop++];
output[k++] = input[ibottom++];
}
// handle last element for N = odd
if (k < N)
output[k] = input[itop];
}
public static void main(String[] args) {
int N = 19;
String[] in = new String[N];
String[] out = new String[N];
for (int i = 0; i < N; ++i)
in[i] = Integer.toString(i);
perfectShuffle(in, out, N);
System.out.println(Arrays.asList(out));
}
}
输出main():
[0, 10, 1, 11, 2, 12, 3, 13, 4, 14, 5, 15, 6, 16, 7, 17, 8, 18, 9]
最后,你不应该用它来洗牌:
public static void main(String[] args) {
int N = 52;
String[] in = new String[N];
String[] out = new String[N];
for (int i = 0; i < N; ++i)
in[i] = Integer.toString(i);
for (int k = 0; k < 8; ++k)
{
perfectShuffle(in, out, N);
System.out.println(Arrays.asList(out));
String[] tmp = in;
in = out;
out = tmp;
}
}
输出:
[0, 26, 1, 27, 2, 28, 3, 29, 4, 30, 5, 31, 6, 32, 7, 33, 8, 34, 9, 35, 10, 36, 11, 37, 12, 38, 13, 39, 14, 40, 15, 41, 16, 42, 17, 43, 18, 44, 19, 45, 20, 46, 21, 47, 22, 48, 23, 49, 24, 50, 25, 51]
[0, 13, 26, 39, 1, 14, 27, 40, 2, 15, 28, 41, 3, 16, 29, 42, 4, 17, 30, 43, 5, 18, 31, 44, 6, 19, 32, 45, 7, 20, 33, 46, 8, 21, 34, 47, 9, 22, 35, 48, 10, 23, 36, 49, 11, 24, 37, 50, 12, 25, 38, 51]
[0, 32, 13, 45, 26, 7, 39, 20, 1, 33, 14, 46, 27, 8, 40, 21, 2, 34, 15, 47, 28, 9, 41, 22, 3, 35, 16, 48, 29, 10, 42, 23, 4, 36, 17, 49, 30, 11, 43, 24, 5, 37, 18, 50, 31, 12, 44, 25, 6, 38, 19, 51]
[0, 16, 32, 48, 13, 29, 45, 10, 26, 42, 7, 23, 39, 4, 20, 36, 1, 17, 33, 49, 14, 30, 46, 11, 27, 43, 8, 24, 40, 5, 21, 37, 2, 18, 34, 50, 15, 31, 47, 12, 28, 44, 9, 25, 41, 6, 22, 38, 3, 19, 35, 51]
[0, 8, 16, 24, 32, 40, 48, 5, 13, 21, 29, 37, 45, 2, 10, 18, 26, 34, 42, 50, 7, 15, 23, 31, 39, 47, 4, 12, 20, 28, 36, 44, 1, 9, 17, 25, 33, 41, 49, 6, 14, 22, 30, 38, 46, 3, 11, 19, 27, 35, 43, 51]
[0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 2, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 3, 7, 11, 15, 19, 23, 27, 31, 35, 39, 43, 47, 51]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51]