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using System.Collections.Generic;
using System.Linq;
namespace aoc2019.lib
{
public static class Extensions
{
public static IEnumerable<IEnumerable<T>> Permute<T>(this IEnumerable<T> list)
{
if (list.Count() == 1) return new[] {list};
return list.SelectMany(t => Permute(list.Where(x => !x.Equals(t))), (v, p) => p.Prepend(v));
}
public static IEnumerable<string> Chunk(this string str, int chunkSize)
{
for (var i = 0; i < str.Length; i += chunkSize)
yield return str.Substring(i, chunkSize);
}
public static string ToDelimitedString<T>(this IEnumerable<T> enumerable, string delimiter = "")
{
return string.Join(delimiter, enumerable);
}
public static IEnumerable<T> Repeat<T>(this IEnumerable<T> sequence, int? count = null)
{
while (count == null || count-- > 0)
foreach (var item in sequence)
yield return item;
}
}
}
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