Perfect shuffle: Difference between revisions

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=={{header|C sharp}}==

{{works with|C sharp|6}}

<lang csharp>using System;

using System.Collections.Generic;

using System.Linq;

public static class PerfectShuffle

{

static void Main()

{

foreach (int input in new [] {8, 24, 52, 100, 1020, 1024, 10000}) {

int[] numbers = Enumerable.Range(1, input).ToArray();

Console.WriteLine($"{input} cards: {ShuffleThrough(numbers).Count()}");

}

IEnumerable<T[]> ShuffleThrough<T>(T[] original) {

T[] copy = (T[])original.Clone();

do {

yield return copy = Shuffle(copy);

} while (!Enumerable.SequenceEqual(original, copy));

}

}

public static T[] Shuffle<T>(T[] array) {

if (array.Length % 2 != 0) throw new ArgumentException("Length must be even.");

int half = array.Length / 2;

T[] result = new T[array.Length];

for (int t = 0, l = 0, r = half; l < half; t+=2, l++, r++) {

result[t] = array[l];

result[t+1] = array[r];

}

return result;

}

}</lang>

{{out}}

<pre>

8 cards: 3

24 cards: 11

52 cards: 8

100 cards: 30

1020 cards: 1018

1024 cards: 10

10000 cards: 300