Java 如何“洗牌”一个数组？
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How to "shuffle" an array?
提问by user2690972
I am having a tough time trying to create a "shuffleDeck()" method.
我在尝试创建“shuffleDeck()”方法时遇到了困难。
What I am trying to do is create a method that will take an array parameter (which will be the deck of cards) shuffle the cards, and return the shuffled array list.
我想要做的是创建一个方法，该方法将采用数组参数（将是一副牌）洗牌，并返回洗牌的数组列表。
This is the code:
这是代码：
class Card
{
int value;
String suit;
String name;
public String toString()
{
return (name + " of " + suit);
}
}
public class PickACard
{
public static void main( String[] args)
{
Card[] deck = buildDeck();
// display Deck(deck);
int chosen = (int)(Math.random()* deck.length);
Card picked = deck[chosen];
System.out.println("You picked a " + picked + " out of the deck.");
System.out.println("In BlackHyman your card is worth " + picked.value + " points.");
}
public static Card[] buildDeck()
{
String[] suits = {"clubs", "diamonds", "hearts", "spades" };
String[] names = {"ZERO", "ONE", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "Hyman", "Queen", "King", "Ace" };
int i = 0;
Card[] deck = new Card[52];
for ( String s: suits )
{
for ( int v = 2; v<=14; v++)
{
Card c = new Card();
c.suit = s;
c.name = names[v];
if ( v == 14)
c.value = 11;
else if ( v>10)
c.value = 10;
else
c.value = v;
deck[i] = c;
i++;
}
}
return deck;
}
public static String[] shuffleDeck( Card[] deck)
{
/** I have attempted to get two index numbers, and swap them.
I tried to figure out how to loop this so it kind of simulates "shuffling".
*/
}
public static void displayDeck( Card[] deck)
{
for ( Card c: deck)
{
System.out.println(c.value + "\t" + c);
}
}
}
回答by rocketboy
How about:
怎么样：
List<Card> list = Arrays.asList(deck);
Collections.shuffle(list);
Or one-liner:
或单线：
Collections.shuffle(Arrays.asList(deck));
回答by Julien
I see two ways to do it:
我看到了两种方法：
-> You can use a shuffle algorithm like the Fisher-Yates shufflealgorithm if you want to implement yourself the method.
->如果你想自己实现这个方法，你可以使用像Fisher-Yatesshuffle 算法这样的shuffle算法。
-> You can use the shuffle method from Collections
-> 您可以使用Collections 中的 shuffle 方法
回答by supertopi
If this is for a school project (as I think it is), you might not be allowed to use built-in functions such as Collections::shuffle(). If this is the case, then you must try to simulate randomness (which in programming can be surprisingly hard).
如果这是用于学校项目（正如我认为的那样），则可能不允许您使用诸如 Collections::shuffle() 之类的内置函数。如果是这种情况，那么您必须尝试模拟随机性（这在编程中可能非常困难）。
The most common way to create a sense of randomness is to use an RNG (random number generator). As you said
创建随机感的最常见方法是使用RNG（随机数生成器）。如你所说
I have attempted to get two index numbers, and swap them.
我试图获得两个索引号，然后交换它们。
Correct. One way to shuffle is to pick one card at a time and randomly select another card to swap the position with.
正确的。一种洗牌方法是一次选择一张牌，然后随机选择另一张牌来交换位置。
- You know the deck always has 52 cards.
- You have a random generator to select a random index.
- You have a programming language with loop-structures.
- 你知道一副牌总是有 52 张牌。
- 您有一个随机生成器来选择一个随机索引。
- 你有一种带有循环结构的编程语言。
With these tools you can implement your own shuffle-function quite easily.
使用这些工具，您可以很容易地实现自己的随机播放功能。
回答by Kevin Cruijssen
One way is to convert the array to a list, and use java.util.Collections.shuffle(array)to shuffle it:
一种方法是将数组转换为列表，并使用java.util.Collections.shuffle(array)shuffle 它：
Card[] deck = ...;
List<Card> list = Arrays.asList(deck);
Collections.shuffle(list);
If you do still need an array instead of a List, you can add:
如果你仍然需要一个数组而不是一个列表，你可以添加：
list.toArray(deck);
Here is a TIO (Try-it-online) link to see the array to list conversion and shuffling in action.
这是一个 TIO (Try-it-online) 链接，用于查看列出转换和改组操作的数组。
Code of the TIO copied below as reference:
下面复制的 TIO 代码作为参考：
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
class M{
public static void main(String[] a){
// Original array
Integer[] array = new Integer[]{ 1, 2, 3, 4, 5, 6, 7, 8, 9 };
System.out.println("before: " + Arrays.toString(array));
// Convert array to list
List<Integer> list = Arrays.asList(array);
// And shuffle that list
Collections.shuffle(list);
System.out.println("after as list: " + list);
// (Optional) then convert the list back to an array,
// and save it in its initial variable (`array` in this case)
list.toArray(array);
System.out.println("after as array: " + Arrays.toString(array));
}
}
