從沒有替換的列表中選擇一個隨機字符串C＃

Question

我有一個字符串列表，我想隨機從這個列表中選擇。當選擇一個字符串時，必須從列表中刪除。只有當所有的字符串被挑選出來後，列表中的纔會重新填充。我如何實現這一目標？

Answer 1

首先，製作一個隨機數發生器。

Random rand = new Random(); 

然後，生成一個數字並從列表中刪除該項目。我假設你正在使用System.Collections.Generic.List。

int num = Random.Next(list.Count); 
list.RemoveAt(num); 

Answer 2

可以實現它非常簡單：

public static partial class EnumerableExtensions { 
    public static IEnumerable<T> RandomItemNoReplacement<T>(this IEnumerable<T> source, 
     Random random) { 

     if (null == source) 
     throw new ArgumentNullException("source"); 
     else if (null == random) 
     throw new ArgumentNullException("random"); 

     List<T> buffer = new List<T>(source); 

     if (buffer.Count <= 0) 
     throw new ArgumentOutOfRangeException("source"); 

     List<T> urn = new List<T>(buffer.Count); 

     while (true) { 
     urn.AddRange(buffer); 

     while (urn.Any()) { 
      int index = random.Next(urn.Count); 

      yield return urn[index]; 

      urn.RemoveAt(index); 
     } 
     } 
    } 
    } 

，然後使用它：

private static Random gen = new Random();  

... 

var result = new List<string>() {"A", "B", "C", "D"} 
    .RandomItemNoReplacement(gen) 
    .Take(10); 

// D, C, B, A, C, A, B, D, A, C (seed == 123) 
Console.Write(string.Join(", ", result)); 

Answer 3

我想，你需要somethink喜歡隔壁班：

public class RandomlyPickedWord 
    { 
     public IList<string> SourceWords{ get; set; } 

     protected IList<string> Words{ get; set; } 

     public RandomlyPickedWord(IList<string> sourceWords) 
     { 
      SourceWords = sourceWords; 
     } 

     protected IList<string> RepopulateWords(IList<string> sources) 
     { 
      Random randomizer = new Random(); 
      IList<string> returnedValue; 
      returnedValue = new List<string>(); 

      for (int i = 0; i != sources.Count; i++) 
      { 
       returnedValue.Add (sources [randomizer.Next (sources.Count - 1)]); 
      } 

      return returnedValue; 
     } 

     public string GetPickedWord() 
     { 
      Random randomizer = new Random(); 
      int curIndex; 
      string returnedValue; 

      if ((Words == null) || (Words.Any() == false)) 
      { 
       Words = RepopulateWords (SourceWords); 
      } 

      curIndex = randomizer.Next (Words.Count); 
      returnedValue = Words [curIndex]; 
      Words.RemoveAt (curIndex); 

      return returnedValue; 
     } 
    } 

你應該用下一個方法：

IList<string> source = new List<string>(); 
      source.Add ("aaa"); 
      source.Add ("bbb"); 
      source.Add ("ccc"); 
      RandomlyPickedWord rndPickedWord = new RandomlyPickedWord (source); 

      for (int i = 0; i != 6; i++) 
      { 
       Console.WriteLine (rndPickedWord.GetPickedWord()); 
      }