如何在链表中洗牌？ [英] How do I shuffle nodes in a linked list?
问题描述
我的头围绕这个方法。特别是当这个作业没有让我们使用任何其他的DATA STRUCTURE或者随机播放方法从java。
所以我有一个Deck.class，其中我已经创建了一个包含52个节点的链接列表，其中包含52个卡。
public class Deck {
private Node theDeck;
private int numCards;
public Deck（）
{
while（numCards< 52）
{
theDeck = new Node（new Card（numCards），theDeck） ;
numCards ++;
}
}
public void shuffleDeck（）
{
int rNum;
int count = 0;
Node current = theDeck;
卡卡;
int range = 0;
while（count！= 51）
{
//在temp变量中存储当前节点内的任何东西
tCard = current.getItem（）;
//生成0-51之间的随机数
rNum =（int）（Math.random（）* 51）;
//在循环上发送一个随机次数
（int i = 0; i
//所以无论当前登陆将该项目存储在该节点中，并将其存储在
theDeck.setItem（current.getItem（））上。
//现在使用开始时的temp变量，并将其存储在当前着陆的地方
current.setItem（tCard）;
//发送当前回到甲板的开头
current = theDeck;
//我为另一个循环创建了一个计数器，我想做
count ++;
//发送一个循环的计数次数，这样它不会刷新已经被洗牌的卡片。 （int i = 0; i< count; i ++）
current = current.getNext（）;
****< - 不能确定这最后一个循环，因为如果我不洗牌已经洗牌的卡不会被视为合法洗牌？我认为？ ****这也是我有时得到一个nullpointerexception ****
}
}
}
现在我收到不同种类的错误
当我调用这个方法：
-
它有时会洗牌只有2张牌，但有时会洗牌3 - 5卡，然后给我一个NullPointerException。
我已经指出，在我上面的代码 -
中，我给出了这个错误的星号，我得到它洗牌13卡，那么每当它做到这一点，它并没有使他们正确的方式洗牌。一张卡总是重复。
-
在另一点我有52张卡片通过while循环，但是再次重复一张卡片。
所以我真的需要一些输入，我做错了什么。在我的代码结束之前，我认为我的逻辑是完全错误的，但我似乎无法想像出来。
sup guys所以我终于弄清楚了，这是我的洗牌方法的更新
public void shuffleDeck（）
{
节点当前;
节点随机;
卡cTemp;
int rand;
rand =（int）（Math.random（）* numCards）; （int i = 0; i< numCards; i ++）
$ b current = theDeck;
random = theDeck;
rand =（int）（Math.random（）* numCards）; （int k = 0; k< rand; k ++）
$ b random = random.getNext（）;
cTemp = current.getItem（）;
current.setItem（random.getItem（））;
random.setItem（cTemp）;
}
}
}
它的工作^ _ ^
感谢输入tho。 =）
I just started a project for my Java2 class and I've come to a complete stop. I just can't get my head around this method. Especially when the assignment does NOT let us use any other DATA STRUCTURE or shuffle methods from java at all.
So I have a Deck.class in which I've already created a linked list containing 52 nodes that hold 52 cards.
public class Deck {
private Node theDeck;
private int numCards;
public Deck ()
{
while(numCards < 52)
{
theDeck = new Node (new Card(numCards), theDeck);
numCards++;
}
}
public void shuffleDeck()
{
int rNum;
int count = 0;
Node current = theDeck;
Card tCard;
int range = 0;
while(count != 51)
{
// Store whatever is inside the current node in a temp variable
tCard = current.getItem();
// Generate a random number between 0 -51
rNum = (int)(Math.random()* 51);
// Send current on a loop a random amount of times
for (int i=0; i < rNum; i ++)
current = current.getNext(); ******<-- (Btw this is the line I'm getting my error, i sort of know why but idk how to stop it.)
// So wherever current landed get that item stored in that node and store it in the first on
theDeck.setItem(current.getItem());
// Now make use of the temp variable at the beginning and store it where current landed
current.setItem(tCard);
// Send current back to the beginning of the deck
current = theDeck;
// I've created a counter for another loop i want to do
count++;
// Send current a "count" amount of times for a loop so that it doesn't shuffle the cards that have been already shuffled.
for(int i=0; i<count; i++)
current = current.getNext(); ****<-- Not to sure about this last loop because if i don't shuffle the cards that i've already shuffled it will not count as a legitimate shuffle? i think? ****Also this is where i sometimes get a nullpointerexception****
}
}
}
Now I get different kinds of errors When I call on this method:
it will sometimes shuffle just 2 cards but at times it will shuffle 3 - 5 cards then give me a NullPointerException. I've pointed out where it gives me this error with asterisks in my code above
at one point I got it to shuffle 13 cards but then everytime it did that it didn't quite shuffle them the right way. one card kept always repeating.
at another point I got all 52 cards to go through the while loop but again it repeated one card various times.
So I really need some input in what I'm doing wrong. Towards the end of my code I think my logic is completely wrong but I can't seem to figure out a way around it.
sup guys so i finally figured it out and this is my update on my shuffle method
public void shuffleDeck()
{
Node current;
Node random;
Card cTemp;
int rand;
rand = (int)(Math.random() * numCards);
for (int j=0; j<rand; j++)
{
for (int i=0; i<numCards; i++)
{
current = theDeck;
random = theDeck;
rand = (int)(Math.random() * numCards);
for(int k = 0; k < rand; k++)
random = random.getNext();
cTemp = current.getItem();
current.setItem(random.getItem());
random.setItem(cTemp);
}
}
}
AND IT WORKS ^_^
Thanks for the input tho. =)
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