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  1. using System;
  2. using System.Linq;
  3. using System.Collections.Generic;
  4.  
  5.     class Foo
  6.     {
  7.        public int A { get; set; }
  8.        public int B { get; set; }
  9.     }
  10.  
  11.     public class GroupOfAdjacent<TSource, TKey> : IEnumerable<TSource>, IGrouping<TKey, TSource>
  12.     {
  13.         public TKey Key { get; set; }
  14.         private List<TSource> GroupList { get; set; }
  15.         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
  16.         {
  17.             return ((System.Collections.Generic.IEnumerable<TSource>)this).GetEnumerator();
  18.         }
  19.         System.Collections.Generic.IEnumerator<TSource> System.Collections.Generic.IEnumerable<TSource>.GetEnumerator()
  20.         {
  21.             foreach (var s in GroupList)
  22.                 yield return s;
  23.         }
  24.         public GroupOfAdjacent(List<TSource> source, TKey key)
  25.         {
  26.             GroupList = source;
  27.             Key = key;
  28.         }
  29.     }
  30.     public static class LocalExtensions
  31.     {
  32.         public static IEnumerable<IGrouping<TKey, TSource>> GroupAdjacent<TSource, TKey>(
  33.             this IEnumerable<TSource> source,
  34.             Func<TSource, TKey> keySelector)
  35.         {
  36.             TKey last = default(TKey);
  37.             bool haveLast = false;
  38.             List<TSource> list = new List<TSource>();
  39.             foreach (TSource s in source)
  40.             {
  41.                 TKey k = keySelector(s);
  42.                 if (haveLast)
  43.                 {
  44.                     if (!k.Equals(last))
  45.                     {
  46.                         yield return new GroupOfAdjacent<TSource, TKey>(list, last);
  47.                         list = new List<TSource>();
  48.                         list.Add(s);
  49.                         last = k;
  50.                     }
  51.                     else
  52.                     {
  53.                         list.Add(s);
  54.                         last = k;
  55.                     }
  56.                 }
  57.                 else
  58.                 {
  59.                     list.Add(s);
  60.                     last = k;
  61.                     haveLast = true;
  62.                 }
  63.             }
  64.             if (haveLast)
  65.                 yield return new GroupOfAdjacent<TSource, TKey>(list, last);
  66.         }
  67.     }
  68.  
  69. public class Test
  70. {
  71.         public static void Main()
  72.         {
  73.            var list = new System.Collections.Generic.List<Foo>(){
  74.                 new Foo(){ A = 1, B = 1 },
  75.                 new Foo(){ A = 1, B = 2 },
  76.                 new Foo(){ A = 2, B = 3 },
  77.                 new Foo(){ A = 2, B = 4 },
  78.                 new Foo(){ A = 1, B = 5 },
  79.                 new Foo(){ A = 3, B = 6 }
  80.             };
  81.  
  82.             var groups = list.GroupAdjacent(x => x.A);
  83.  
  84.             foreach (var abGroup in groups)
  85.             {
  86.                 int aKey = abGroup.Key;
  87.                 var bList = string.Join(",", abGroup.Select(x => x.B.ToString()).ToArray());
  88.                 Console.WriteLine("A = {0}, Bs = [ {1} ] ", aKey, bList);
  89.             }
  90.         }
  91. }
Success #stdin #stdout 0.04s 38064KB
comments (?)
stdin
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Standard input is empty
stdout
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A = 1, Bs = [ 1,2 ] 
A = 2, Bs = [ 3,4 ] 
A = 1, Bs = [ 5 ] 
A = 3, Bs = [ 6 ]
https://ideone.com/XsJzq
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
public

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