c# - 从整数列表中获取随机数

Question

如果我有一个整数列表:

List<int> myValues = new List<int>(new int[] { 1, 2, 3, 4, 5, 6 } );

我如何从该列表中获得 3 个随机整数？

Answer 1

一个简单的方法:

Random r = new Random();
IEnumerable<int> threeRandom = myValues.OrderBy(x => r.Next()).Take(3);

更好的方法:Fisher–Yates shuffle :

public static class EnumerableExtensions
{
    public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> source)
    {
        return source.Shuffle(new Random());
    }

    public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> source, Random rng)
    {
        if (source == null) throw new ArgumentNullException("source");
        if (rng == null) throw new ArgumentNullException("rng");

        return source.ShuffleIterator(rng);
    }

    private static IEnumerable<T> ShuffleIterator<T>(
        this IEnumerable<T> source, Random rng)
    {
        List<T> buffer = source.ToList();
        for (int i = 0; i < buffer.Count; i++)
        {
            int j = rng.Next(i, buffer.Count);
            yield return buffer[j];

            buffer[j] = buffer[i];
        }
    }
}

如何使用它:

IEnumerable<int> threeRandom = myValues.Shuffle().Take(3);