[7812] | 1 | #region License Information
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| 2 | /* HeuristicLab
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[11171] | 3 | * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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[7812] | 4 | *
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| 5 | * This file is part of HeuristicLab.
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| 6 | *
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| 7 | * HeuristicLab is free software: you can redistribute it and/or modify
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| 8 | * it under the terms of the GNU General Public License as published by
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| 9 | * the Free Software Foundation, either version 3 of the License, or
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| 10 | * (at your option) any later version.
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| 11 | *
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| 12 | * HeuristicLab is distributed in the hope that it will be useful,
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| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 15 | * GNU General Public License for more details.
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| 16 | *
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| 17 | * You should have received a copy of the GNU General Public License
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| 18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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| 19 | */
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| 20 | #endregion
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| 21 |
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| 22 | using System;
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| 23 | using System.Collections.Generic;
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| 24 | using System.Linq;
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| 25 |
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| 26 | namespace HeuristicLab.Common {
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| 27 | public static class EnumerableExtensions {
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| 28 | /// <summary>
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| 29 | /// Selects all elements in the sequence that are maximal with respect to the given value.
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| 30 | /// </summary>
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| 31 | /// <remarks>
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| 32 | /// Runtime complexity of the operation is O(N).
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| 33 | /// </remarks>
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| 34 | /// <typeparam name="T">The type of the elements.</typeparam>
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| 35 | /// <param name="source">The enumeration in which the items with a maximal value should be found.</param>
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| 36 | /// <param name="valueSelector">The function that selects the value to compare.</param>
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| 37 | /// <returns>All elements in the enumeration where the selected value is the maximum.</returns>
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| 38 | public static IEnumerable<T> MaxItems<T>(this IEnumerable<T> source, Func<T, IComparable> valueSelector) {
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| 39 | IEnumerator<T> enumerator = source.GetEnumerator();
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| 40 | if (!enumerator.MoveNext()) return Enumerable.Empty<T>();
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| 41 | IComparable max = valueSelector(enumerator.Current);
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| 42 | var result = new List<T>();
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| 43 | result.Add(enumerator.Current);
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| 44 |
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| 45 | while (enumerator.MoveNext()) {
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| 46 | T item = enumerator.Current;
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| 47 | IComparable comparison = valueSelector(item);
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| 48 | if (comparison.CompareTo(max) > 0) {
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| 49 | result.Clear();
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| 50 | result.Add(item);
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| 51 | max = comparison;
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| 52 | } else if (comparison.CompareTo(max) == 0) {
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| 53 | result.Add(item);
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| 54 | }
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| 55 | }
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| 56 | return result;
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| 57 | }
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| 58 |
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| 59 | /// <summary>
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| 60 | /// Selects all elements in the sequence that are minimal with respect to the given value.
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| 61 | /// </summary>
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| 62 | /// <remarks>
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| 63 | /// Runtime complexity of the operation is O(N).
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| 64 | /// </remarks>
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| 65 | /// <typeparam name="T">The type of the elements.</typeparam>
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| 66 | /// <param name="source">The enumeration in which items with a minimal value should be found.</param>
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| 67 | /// <param name="valueSelector">The function that selects the value.</param>
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| 68 | /// <returns>All elements in the enumeration where the selected value is the minimum.</returns>
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| 69 | public static IEnumerable<T> MinItems<T>(this IEnumerable<T> source, Func<T, IComparable> valueSelector) {
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| 70 | IEnumerator<T> enumerator = source.GetEnumerator();
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| 71 | if (!enumerator.MoveNext()) return Enumerable.Empty<T>();
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| 72 | IComparable min = valueSelector(enumerator.Current);
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| 73 | var result = new List<T>();
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| 74 | result.Add(enumerator.Current);
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| 75 |
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| 76 | while (enumerator.MoveNext()) {
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| 77 | T item = enumerator.Current;
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| 78 | IComparable comparison = valueSelector(item);
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| 79 | if (comparison.CompareTo(min) < 0) {
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| 80 | result.Clear();
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| 81 | result.Add(item);
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| 82 | min = comparison;
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| 83 | } else if (comparison.CompareTo(min) == 0) {
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| 84 | result.Add(item);
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| 85 | }
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| 86 | }
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| 87 | return result;
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| 88 | }
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[11309] | 89 |
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| 90 | /// <summary>
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| 91 | /// Compute the n-ary cartesian product of arbitrarily many sequences: http://blogs.msdn.com/b/ericlippert/archive/2010/06/28/computing-a-cartesian-product-with-linq.aspx
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| 92 | /// </summary>
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| 93 | /// <typeparam name="T">The type of the elements inside each sequence</typeparam>
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| 94 | /// <param name="sequences">The collection of sequences</param>
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| 95 | /// <returns>An enumerable sequence of all the possible combinations of elements</returns>
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| 96 | public static IEnumerable<IEnumerable<T>> CartesianProduct<T>(this IEnumerable<IEnumerable<T>> sequences) {
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| 97 | IEnumerable<IEnumerable<T>> result = new[] { Enumerable.Empty<T>() };
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| 98 | return sequences.Aggregate(result, (current, s) => (from seq in current from item in s select seq.Concat(new[] { item })));
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| 99 | }
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[7812] | 100 | }
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| 101 | }
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