计算字符串中特定字符的出现次数

Question

计算字符串中特定字符出现次数的最简单方法是什么？

即我需要编写一个函数countTheCharacters（），使

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

Answer 1

最直接的方式是简单地通过字符串中的字符循环：

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并且代码更短的方法就是给我们ËLINQ扩展方法：

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

Answer 2

另一种可能性是与斯普利特的工作：

Dim tmp() As String 
tmp = Split(Expression, Delimiter) 
Dim count As Integer = tmp.Length - 1 

Answer 3

另一种可能性是使用正则表达式：

string a = "this is test"; 
string pattern = "t"; 
System.Text.RegularExpressions.Regex ex = new System.Text.RegularExpressions.Regex(pattern); 
System.Text.RegularExpressions.MatchCollection m = ex.Matches(a); 
MessageBox.Show(m.Count.ToString()); 

请转换为VB.NET这。

Answer 4

或（在VB.NET）：

Function InstanceCount(ByVal StringToSearch As String, 
         ByVal StringToFind As String) As Long 
    If Len(StringToFind) Then 
     InstanceCount = UBound(Split(StringToSearch, StringToFind)) 
    End If 
End Function 

Answer 5

这里是直接代码解决了OP的问题：

 Dim str As String = "the little red hen" 

     Dim total As Int32 

     Dim Target As String = "e" 
     Dim Temp As Int32 
     Dim Temp2 As Int32 = -1 
Line50: 
     Temp = str.IndexOf(Target, Temp2 + 1) 
     Temp2 = Temp 
     If Temp <> -1 Then 

      ' Means there is a target there 
      total = total + 1 
      GoTo Line50 
     End If 

     MessageBox.Show(CStr(total)) 

现在，这是一个方便的功能，解决了OP的问题：使用功能的

Public Function CountOccurrence(ByVal YourStringToCountOccurrence As String, ByVal TargetSingleCharacterToCount As String) As Int32 
     Dim total As Int32 

     Dim Temp As Int32 
     Dim Temp2 As Int32 = -1 
Line50: 
     Temp = YourStringToCountOccurrence.IndexOf(TargetSingleCharacterToCount, Temp2 + 1) 
     Temp2 = Temp 
     If Temp <> -1 Then 

      ' Means there is a target there 
      total = total + 1 
      GoTo Line50 
     Else 
      Return total 
     End If 
    End Function 

实施例：

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click 
    Dim str As String = "the little red hen" 

    MessageBox.Show(CStr(CountOccurrence(str, "e"))) 
    ' It will return 4 
End Sub 

Answer 6

将Ujjwal Manandhar的代码转换为VB.NET，如下所示...

Dim a As String = "this is test" 
Dim pattern As String = "t" 
Dim ex As New System.Text.RegularExpressions.Regex(pattern) 
Dim m As System.Text.RegularExpressions.MatchCollection 
m = ex.Matches(a) 
MsgBox(m.Count.ToString()) 

Answer 7

你可以试试这个

Dim occurCount As Integer = Len(testStr) - Len(testStr.Replace(testCharStr, "")) 

Answer 8

Public Function CountOccurrences(ByVal StToSerach As String, ByVal StToLookFor As String) As Int32 

    Dim iPos = -1 
    Dim iFound = 0 
    Do 
     iPos = StToSerach.IndexOf(StToLookFor, iPos + 1) 
     If iPos <> -1 Then 
      iFound += 1 
     End If<br/> 
    Loop Until iPos = -1 
    Return iFound 
End Function 

代码使用：

Dim iCountTimes As Integer = CountOccurrences("Can I call you now?", "a") 

你也可以把它作为一个扩展：

<Extension()> _ 
Public Function CountOccurrences(ByVal StToSerach As String, ByVal StToLookFor As String) As Int32 
    Dim iPos = -1 
    Dim iFound = 0 
    Do 
     iPos = StToSerach.IndexOf(StToLookFor, iPos + 1) 
     If iPos <> -1 Then 
      iFound += 1 
     End If 
    Loop Until iPos = -1 
    Return iFound 
End Function 

代码使用：

Dim iCountTimes2 As Integer = "Can I call you now?".CountOccurrences("a") 

Answer 9

这是简单的方式

text="the little red hen" 
count = text.Split("e").Length -1 ' Equals 4 
count = text.Split("t").Length -1 ' Equals 3 

Answer 10

Public Class VOWELS 

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
     Dim str1, s, c As String 
     Dim i, l As Integer 
     str1 = TextBox1.Text 
     l = Len(str1) 
     c = 0 
     i = 0 
     Dim intloopIndex As Integer 
     For intloopIndex = 1 To l 
      s = Mid(str1, intloopIndex, 1) 
      If (s = "A" Or s = "a" Or s = "E" Or s = "e" Or s = "I" Or s = "i" Or s = "O" Or s = "o" Or s = "U" Or s = "u") Then 
       c = c + 1 
      End If 
     Next 
     MsgBox("No of Vowels: " + c.ToString) 
    End Sub 
End Class 

Answer 11

当我发现这个解决方案，我一直在寻找的东西，因为我想算字符串略有不同的是长于一个字符，所以我想出了这个解决方案：

Public Shared Function StrCounter(str As String, CountStr As String) As Integer 
     Dim Ctr As Integer = 0 
     Dim Ptr As Integer = 1 
     While InStr(Ptr, str, CountStr) > 0 
      Ptr = InStr(Ptr, str, CountStr) + Len(CountStr) 
      Ctr += 1 
     End While 
     Return Ctr 
    End Function 

Answer 12

我建议你这样做：

String.Replace("e", "").Count 
String.Replace("t", "").Count 

您还可以使用.Split("e").Count - 1或.Split("t").Count - 1 respetivelly，但它给错误的价值观，如果你，比如有一个E或处的String

Answer 13

开始我找到了最好的答案：P：

String.ToString.Count - String.ToString.Replace("e", "").Count 
String.ToString.Count - String.ToString.Replace("t", "").Count 

Answer 14

使用正则表达式...

Public Function CountCharacter(ByVal value As String, ByVal ch As Char) As Integer 
    Return (New System.Text.RegularExpressions.Regex(ch)).Matches(value).Count 
End Function 

Answer 15

'trying to find the amount of "." in the text 
    'if txtName looks like "hi...hi" then intdots will = 3 
    Dim test As String = txtName.Text 
    Dim intdots As Integer = 0 
    For i = 1 To test.Length 
     Dim inta As Integer = 0 + 1 
     Dim stra As String = test.Substring(inta) 
     If stra = "." Then 
      intdots = intdots + 1 
     End If 
    Next 
    txttest.text = intdots 

Answer 16

我使用LINQ，而解决的方法很简单：在C＃

代码：

count = yourString.ToCharArray().Count(c => c == 'e'); 

在一个函数的代码：

public static int countTheCharacters(string str, char charToCount){ 
    return str.ToCharArray().Count(c => c == charToCount); 
} 

调用该函数：

count = countTheCharacters(yourString, 'e'); 

Answer 17

使用：

Dim a 
inputString = InputBox("Enter String", "Enter Value", "") 

MyString = UCase(inputString) 

MsgBox MyString 

Dim stringLength 

stringLength = Len(MyString) 

Dim temp 

output = "" 

i = 1 
Do 
    temp = Mid(MyString, i, 1) 

    MsgBox temp & i 

    CharacterCount = len(MyString) - len(Replace(MyString, temp, "")) 

    MyString = Replace(MyString, temp, "") 

    output = output & temp & ": " & CharacterCount & vbNewline 

Loop While MyString <> "" 

MsgBox output 

Answer 18

我认为这将是最简单的：

Public Function CountCharacter(ByVal value As String, ByVal ch As Char) As Integer 
    Return len(value) - len(replace(value, ch, "")) 
End Function 

Answer 19

下面是一个简单的版本。

text.count(function(x) x = "a") 

上面会给你字符串中a的个数。如果你想忽略大小写：

text.count(function(x) Ucase(x) = "A") 

或者，如果你只是想算字母：

text.count(function(x) Char.IsLetter(x) = True) 

给它一个镜头！

Answer 20

Private Sub Data_KeyPress(sender As Object, e As KeyPressEventArgs) Handles Data.KeyPress 
    If Not IsNumeric(e.KeyChar) And Not e.KeyChar = ChrW(Keys.Back) And Not e.KeyChar = "." Then 
     e.Handled = True 
    Else 
     If e.KeyChar = "." And Data.Text.ToCharArray().Count(Function(c) c = ".") > 0 Then 
      e.Handled = True 
     End If 
    End If 
End Sub 

Answer 21

用途：

Function fNbrStrInStr(strin As Variant, strToCount As String) 
    fNbrStrInStr = UBound(Split(strin, strToCount)) - LBound(Split(strin, strToCount)) 
End Function 

我以前strin的变种来处理很长的文本。根据用户设置，拆分可以是基于零的或基于一个的，并且减去它可以确保正确的计数。

为了保持代码的简洁，我没有包含对strcount的测试长于strin。

Answer 22

eCount = str.Length - Replace(str, "e", "").Length 
tCount = str.Length - Replace(str, "t", "").Length 

Answer 23

什么巨大的代码这么简单的东西：

在C＃中，创建一个扩展方法和使用LINQ。

public static int CountOccurences(this string s, char c) 
{ 
    return s.Count(t => t == c); 
} 

用法：

int count = "toto is the best".CountOccurences('t'); 

结果：4

Answer 24

var charCount = "string with periods...".Count(x => '.' == x);

Answer 25

谢谢，@guffa。在一行中执行，或者在.NET中执行更长的语句的能力非常方便。此VB.NET示例计算LineFeed字符的数量：

Dim j As Integer = MyString.Count(Function(c As Char) c = vbLf) 

j返回MyString中LineFeeds的数量。

Answer 26

我使用以下函数。它不是最高效的内存，但它很容易理解，支持多种比较方法，只有4行，速度很快，大多数在VBA中也可以工作，不仅可以找到单个字符，而且还可以找到任何搜索字符串（我经常搜索VbCrLf （一个或多个））。

唯一缺少的是从一个不同的“开始”开始搜索能力

Function inStC(myInput As String, Search As String, Optional myCompareMethod As Long = CompareMethod.Text) As Long 
     If InStr(1, myInput, Search, myCompareMethod) = 0 Then Return 0 
     Return UBound(Split(myInput, Search,, myCompareMethod)) 
    End Function 

有一件事我喜欢的是它体积小巧使用的例子。

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

虽然我在这里，我想抬价我inStB功能，其中，而不是返回一个字符串的计数，它只会返回一个布尔值，如果搜索字符串是存在的。我经常需要这个函数，这使得我的代码更加清晰。

Function inStB(myInput As String, Search As String, Optional Start As Long = 1, Optional myCompareMethod As Long = CompareMethod.Text) As Boolean 
    If InStr(Start, myInput, Search, myCompareMethod) > 0 Then Return True 
    Return False 
End Function