数组改组不起作用
我正在尝试编写代码来在不使用集合的情况下对数组进行洗牌。
我的洗牌代码
是
private double amounts[] = { 0, 0.01, 1000000, 25, 250000, 75, 50, 1000,
200, 100, 400000, 750, 5000, 750000, 500, 100000, 300, 75000, 800,
20, 300000, 10, 50, 750, 25, 5, 1 };
public void Shuffle(){
Random rgen = new Random();
for (int i=0; i > amounts.length; i++) {
int randomPosition = rgen.nextInt(amounts.length);
double temp = amounts[i];
amounts[i] = amounts[randomPosition];
amounts[randomPosition] = temp;
}
}
启动它的代码
public void casesSetup() {
for (int i = 0; i < briefcase.length; i++) {
if (i == 0) {
} else {
briefcase[i] = new Briefcase();
double value = amounts[i];
briefcase[i].setAmount(value);
briefcase[i].setFace(i);
}
}
}
我的问题是它们没有被随机化有人知道为什么吗？
I am trying to write code to shuffle an Array without using Collections.
My shuffle code
the Amounts
private double amounts[] = { 0, 0.01, 1000000, 25, 250000, 75, 50, 1000,
200, 100, 400000, 750, 5000, 750000, 500, 100000, 300, 75000, 800,
20, 300000, 10, 50, 750, 25, 5, 1 };
public void Shuffle(){
Random rgen = new Random();
for (int i=0; i > amounts.length; i++) {
int randomPosition = rgen.nextInt(amounts.length);
double temp = amounts[i];
amounts[i] = amounts[randomPosition];
amounts[randomPosition] = temp;
}
}
the code that initiates it
public void casesSetup() {
for (int i = 0; i < briefcase.length; i++) {
if (i == 0) {
} else {
briefcase[i] = new Briefcase();
double value = amounts[i];
briefcase[i].setAmount(value);
briefcase[i].setFace(i);
}
}
}
my problem here is that they are not being randomized anyone has an idea why?
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评论（4）
第一个片段中的 for 循环似乎是错误的，
不是吗？
for loop in your first snippet seem to be wrong
shouldn't it be
将值存储在列表中并使用
Collections.shuffle http: //download.oracle.com/javase/6/docs/api/java/util/Collections.html#shuffle(java.util.List)
自己手动滚动似乎没有必要
Store the values in a List and use
Collections.shuffle http://download.oracle.com/javase/6/docs/api/java/util/Collections.html#shuffle(java.util.List)
Hand rolling this on your own seems unnecesary
我的建议是开始反向洗牌：
假设 Random.nextInt(N) 的分布在 0..N-1 上是均匀的，这将对数组进行洗牌，每个排列的可能性均等。对此的论证是直截了当的。
My tip is to start shuffling in reverse:
Assuming that the distribution of Random.nextInt(N) is uniform on 0..N-1 this will shuffle your array with each permutation being equally as likely. The argumentation for that is straight forward.
除了 for 循环错误之外，您还应该更改
为
以获得均匀的随机分布。
In addition to your for loop being wrong, you should change
to
to get a uniform random distribution.