46 lines
1.5 KiB
C#
46 lines
1.5 KiB
C#
using System.Diagnostics;
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namespace aoc2019;
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public static class Extensions
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{
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public static IEnumerable<IEnumerable<T>> Permute<T>(this IEnumerable<T> list)
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{
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if (list.Count() == 1) return new[] { list };
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return list.SelectMany(t => Permute(list.Where(x => !x!.Equals(t))), (v, p) => p.Prepend(v));
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}
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public static IEnumerable<string> Chunk(this string str, int chunkSize)
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{
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for (var i = 0; i < str.Length; i += chunkSize)
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yield return str.Substring(i, chunkSize);
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}
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public static string ToDelimitedString<T>(this IEnumerable<T> enumerable, string delimiter = "")
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{
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return string.Join(delimiter, enumerable);
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}
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public static IEnumerable<T> Repeat<T>(this IEnumerable<T> sequence, int? count = null)
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{
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while (count == null || count-- > 0)
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foreach (var item in sequence)
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yield return item;
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}
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/// <summary>
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/// increased accuracy for stopwatch based on frequency.
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/// <see
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/// href="http://geekswithblogs.net/BlackRabbitCoder/archive/2012/01/12/c.net-little-pitfalls-stopwatch-ticks-are-not-timespan-ticks.aspx">
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/// blog
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/// details here
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/// </see>
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/// </summary>
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/// <param name="stopwatch"></param>
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/// <returns></returns>
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public static double ScaleMilliseconds(this Stopwatch stopwatch)
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{
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return 1_000 * stopwatch.ElapsedTicks / (double)Stopwatch.Frequency;
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}
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}
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