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  1. using System;
  2. using System.Collections.Generic;
  3.  
  4. public static class RandomElementSelector
  5. {
  6.     public static IList<T> CollectAllowedElements<T>(IList<T> allElements, IList<T> excludedElements)
  7.     {
  8.         List<T> allowedElements = new List<T>();
  9.         foreach (T element in allElements)
  10.             if (!excludedElements.Contains(element))
  11.                 allowedElements.Add(element);
  12.         return allowedElements;
  13.     }
  14.  
  15.     public static T SelectRandomElement<T>(IList<T> allowedElements)
  16.     {
  17.         Random random = new Random();
  18.         int randomIndex = random.Next(allowedElements.Count);
  19.         return allowedElements[randomIndex];
  20.     }
  21.  
  22.     public static T SelectRandomElement<T>(IList<T> allElements, IList<T> excludedElements)
  23.     {
  24.         IList<T> allowedElements = CollectAllowedElements(allElements, excludedElements);
  25.         return SelectRandomElement(allowedElements);
  26.     }
  27. }
  28.  
  29. public class Test
  30. {
  31.     public static void Main()
  32.     {
  33.         const int N = 100;
  34.  
  35.         // Example #1
  36.         int[] allNumbers = new int[N];
  37.         for (int i = 0; i < allNumbers.Length; ++i)
  38.             allNumbers[i] = i + 1;
  39.         int[] excludedNumbers = { 5, 7, 17, 23 };
  40.         Console.WriteLine(RandomElementSelector.SelectRandomElement(allNumbers, excludedNumbers));
  41.  
  42.         // Example #2
  43.         List<string> allStrings = new List<string>();
  44.         for (int i = 0; i < N; ++i)
  45.             allStrings.Add("Item #" + (i + 1));
  46.         string[] excludedStrings = { "Item #5", "Item #7", "Item #17", "Item #23" };
  47.         Console.WriteLine(RandomElementSelector.SelectRandomElement(allStrings, excludedStrings));
  48.         }
  49. }
Success #stdin #stdout 0.03s 33928KB
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48
Item #21
https://ideone.com/toHMQ8
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
public

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