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using System.Collections.Generic;
using System.Diagnostics;
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;
}
/// <summary>
/// increased accuracy for stopwatch based on frequency.
/// <see
/// href="http://geekswithblogs.net/BlackRabbitCoder/archive/2012/01/12/c.net-little-pitfalls-stopwatch-ticks-are-not-timespan-ticks.aspx">
/// blog
/// details here
/// </see>
/// </summary>
/// <param name="stopwatch"></param>
/// <returns></returns>
public static double ScaleMilliseconds(this Stopwatch stopwatch)
{
return 1_000 * stopwatch.ElapsedTicks / (double) Stopwatch.Frequency;
}
}
}
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