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Add MinByWithTies and MaxByWithTies to bring back a MinBy/MaxBy that …
…returns a list.
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Ix.NET/Source/System.Interactive/System/Linq/Operators/MaxByWithTies.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,84 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT License. | ||
| // See the LICENSE file in the project root for more information. | ||
|
|
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| using System.Collections.Generic; | ||
|
|
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| namespace System.Linq | ||
| { | ||
| public static partial class EnumerableEx | ||
| { | ||
| /// <summary> | ||
| /// Returns the elements with the maximum key value by using the default comparer to compare key values. | ||
| /// </summary> | ||
| /// <typeparam name="TSource">Source sequence element type.</typeparam> | ||
| /// <typeparam name="TKey">Key type.</typeparam> | ||
| /// <param name="source">Source sequence.</param> | ||
| /// <param name="keySelector">Key selector used to extract the key for each element in the sequence.</param> | ||
| /// <returns>List with the elements that share the same maximum key value.</returns> | ||
| public static IList<TSource> MaxByWithTies<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) | ||
| { | ||
| if (source == null) | ||
| throw new ArgumentNullException(nameof(source)); | ||
| if (keySelector == null) | ||
| throw new ArgumentNullException(nameof(keySelector)); | ||
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| return MaxByWithTies(source, keySelector, Comparer<TKey>.Default); | ||
| } | ||
|
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| /// <summary> | ||
| /// Returns the elements with the minimum key value by using the specified comparer to compare key values. | ||
| /// </summary> | ||
| /// <typeparam name="TSource">Source sequence element type.</typeparam> | ||
| /// <typeparam name="TKey">Key type.</typeparam> | ||
| /// <param name="source">Source sequence.</param> | ||
| /// <param name="keySelector">Key selector used to extract the key for each element in the sequence.</param> | ||
| /// <param name="comparer">Comparer used to determine the maximum key value.</param> | ||
| /// <returns>List with the elements that share the same maximum key value.</returns> | ||
| public static IList<TSource> MaxByWithTies<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IComparer<TKey> comparer) | ||
| { | ||
| if (source == null) | ||
| throw new ArgumentNullException(nameof(source)); | ||
| if (keySelector == null) | ||
| throw new ArgumentNullException(nameof(keySelector)); | ||
| if (comparer == null) | ||
| throw new ArgumentNullException(nameof(comparer)); | ||
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| return ExtremaBy(source, keySelector, (key, minValue) => comparer.Compare(key, minValue)); | ||
| } | ||
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| private static IList<TSource> ExtremaBy<TSource, TKey>(IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TKey, TKey, int> compare) | ||
| { | ||
| var result = new List<TSource>(); | ||
|
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| using (var e = source.GetEnumerator()) | ||
| { | ||
| if (!e.MoveNext()) | ||
| throw new InvalidOperationException("Source sequence doesn't contain any elements."); | ||
|
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| var current = e.Current; | ||
| var resKey = keySelector(current); | ||
| result.Add(current); | ||
|
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| while (e.MoveNext()) | ||
| { | ||
| var cur = e.Current; | ||
| var key = keySelector(cur); | ||
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| var cmp = compare(key, resKey); | ||
| if (cmp == 0) | ||
| { | ||
| result.Add(cur); | ||
| } | ||
| else if (cmp > 0) | ||
| { | ||
| result = new List<TSource> { cur }; | ||
| resKey = key; | ||
| } | ||
| } | ||
| } | ||
|
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| return result; | ||
| } | ||
| } | ||
| } |
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