计算字符串中特定字符的出现次数 [英] Count specific character occurrences in a string

问题描述

计算字符串中特定字符出现次数的最简单方法是什么?

What is the simplest way to count the number of occurrences of a specific character in a string?

也就是说，我需要写一个函数，countTheCharacters()，以便

That is, I need to write a function, countTheCharacters(), so that

str = "the little red hen"
count = countTheCharacters(str,"e") ' Count should equal 4
count = countTheCharacters(str,"t") ' Count should equal 3

推荐答案

最直接的就是简单地循环遍历字符串中的字符:

The most straightforward is to simply loop through the characters in the string:

Public Function CountCharacter(ByVal value As String, ByVal ch As Char) As Integer
  Dim cnt As Integer = 0
  For Each c As Char In value
    If c = ch Then 
      cnt += 1
    End If
  Next
  Return cnt
End Function

用法:

count = CountCharacter(str, "e"C)

另一种几乎同样有效且代码更短的方法是使用 LINQ 扩展方法:

Another approach that is almost as effective and gives shorter code is to use LINQ extension methods:

Public Function CountCharacter(ByVal value As String, ByVal ch As Char) As Integer
  Return value.Count(Function(c As Char) c = ch)
End Function

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