C#中使用基数排序算法对字符串进行排序的示例

//字符集
private string _myCharSet = "0123456789qwertyuiopasdfghjklzxcvbnm";

private Random _random = new Random();
 
string[] GetRandStrings(int size, int minLength, int maxLength)
{
  string[] strs = new string[size];
  int len = 0;
  StringBuilder sb = new StringBuilder(maxLength);
 
  for (int i = 0; i < strs.Length; i++)
  {
    //先随机确定一个长度
    len = _random.Next(minLength, maxLength);
    for (int j = 0; j < len; j++)
    {
      //随机选取一个字符
      sb.Append(_myCharSet[_random.Next(_myCharSet.Length)]);
    }
    strs[i] = sb.ToString();
    sb.Clear();
  }
  return strs;
}

void StringRadixSort(string[] strArray)
{
  if (strArray == null
    || strArray.Length == 0
    || strArray.Contains(null))
  {
    return;
  }
 
  //获得字符串的最大长度
  int maxLength = 0;
  foreach (string s in strArray)
  {
    if (s.Length > maxLength)
    {
      maxLength = s.Length;
    }
  }
 
  //确定字符的整数范围
  int rangeStart = _myCharSet[0];
  int rangeEnd = _myCharSet[0];
  foreach (char ch in _myCharSet)
  {
    if (ch < rangeStart)
      rangeStart = ch;
    if (ch >= rangeEnd)
      rangeEnd = ch + 1;
  }
 
  //也要为"空字符"分配一个桶，其索引为0
  int bucketCount = rangeEnd - rangeStart + 1;
  LinkedList<string>[] buckets = new LinkedList<string>[bucketCount];
 
  //初始化所有的桶
  for (int i = 0; i < buckets.Length; i++)
  {
    buckets[i] = new LinkedList<string>();
  }
 
  //从最后一个字符开始排序
  int currentIndex = maxLength - 1;
  while (currentIndex >= 0)
  {
    foreach (string theString in strArray)
    {
      //如果超出索引，返回'\0'字符(default(char))
      char ch = theString.ElementAtOrDefault(currentIndex);
      if (ch == default(char))
      {  //"空字符"的处理
        buckets[0].AddLast(theString);
      }
      else
      {  //将字符映射到桶
        int index = ch - rangeStart + 1;
        buckets[index].AddLast(theString);
      }
    }
    //从桶里依次取回字符串，完成一趟排序
    int i = 0;
    foreach (LinkedList<string> bucket in buckets)
    {
      while (bucket.Count > 0)
      {
        strArray[i++] = bucket.First();
        bucket.RemoveFirst();
      }
    }
    currentIndex--;
  }
}

private Dictionary<char, int> _charOrderDict = 
        new Dictionary<char, int>(_myCharSet.Length);
void BuildCharOrderDict()
{
  char[] sortedCharSet = _myCharSet.ToArray();
  //使用默认的比较器排序
  Array.Sort(sortedCharSet);
  //为"空字符"单独创建映射
  _charOrderDict.Add(default(char), 0);
  for (int i = 0; i < sortedCharSet.Length; i++)
  {
    // 保存的是字符及其对应的桶的索引
    _charOrderDict.Add(sortedCharSet[i], i + 1);
  }
}

void StringRadixSort(string[] strArray)
{
  if (strArray == null
    || strArray.Length == 0
    || strArray.Contains(null))
  {
    return;
  }
  //获得字符串的最大长度
  int maxLength = 0;
  foreach (string s in strArray)
  {
    if (s.Length > maxLength)
    {
      maxLength = s.Length;
    }
  }
 
  //为每一个字符(包括空字符'\0')分配一个桶
  //"空字符"索引应为0
  int bucketCount = _myCharSet.Length + 1;
  LinkedList<string>[] buckets = new LinkedList<string>[bucketCount];
 
  //初始化所有的桶
  for (int i = 0; i < buckets.Length; i++)
  {
    buckets[i] = new LinkedList<string>();
  }
 
  //从最后一个字符开始排序
  int currentIndex = maxLength - 1;
  while (currentIndex >= 0)
  {
    foreach (string theString in strArray)
    {
      //如果超出索引，返回'\0'字符(default(char))
      char ch = theString.ElementAtOrDefault(currentIndex);
      //根据字符顺序的定义查询字符
      int index = _charOrderDict[ch];
      buckets[index].AddLast(theString);
    }
    //从桶里依次取回字符串，完成一趟排序
    int i = 0;
    foreach (LinkedList<string> bucket in buckets)
    {
      while (bucket.Count > 0)
      {
        strArray[i++] = bucket.First();
        bucket.RemoveFirst();
      }
    }
    currentIndex--;
  }
}