如何有效地从1到50中选择几个唯一的随机数(不包括x)? [英] How can I efficiently select several unique random numbers from 1 to 50, excluding x?

问题描述

我有2个数字，介于0和49之间.我们称它们为x和y.现在，我想获得几个其他的数字，它们不是x或y，但也都在0和49之间(我使用的是Objective C，但这更多是我认为的一般理论问题?).

我想到的方法是:

 int a;
 int b;
 int c;

 do {
  a = arc4random() % 49;
 } while ((a == x) || (a == y));

 do {
  b = arc4random() % 49;
 } while ((b == x) || (b == y) || (b == a));

 do {
  c = arc4random() % 49;
 } while ((c == x) || (c == y) || (c == a) || (c == b));

但这对我来说似乎有点不好，我不知道，我只是想学习成为一个更好的程序员，对于最佳实践而言，最优雅的方法是什么?

解决方案

您可以使用 Fisher-Yates洗牌.这是一种有效的算法，可以从某个集合中生成一个随机排序的值列表.您首先要从要获取随机值的值列表中排除N，然后执行随机播放.

I have 2 numbers which are between 0 and 49. Let's call them x and y. Now I want to get a couple of other numbers which are not x or y, but are also between 0 and 49 (I am using Objective C but this is more of a general theory question I think?).

Method I thought of is:

 int a;
 int b;
 int c;

 do {
  a = arc4random() % 49;
 } while ((a == x) || (a == y));

 do {
  b = arc4random() % 49;
 } while ((b == x) || (b == y) || (b == a));

 do {
  c = arc4random() % 49;
 } while ((c == x) || (c == y) || (c == a) || (c == b));

But it seem kind of bad to me, I don't know, I am just trying to learn to be a better programmer, what would be the most elegant way to do this for best practices?

解决方案

You can use something called the Fisher-Yates shuffle. It's an efficient algorithm for producing a randomly ordered list of values from some set. You would first exclude N from the list of values from which to get random values, and then perform the shuffle.

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