计算string中特定的字符出现次数
计算string中特定字符出现次数的最简单方法是什么？
即我需要写一个函数countTheCharacters（），以便
str="the little red hen" count=countTheCharacters(str,"e") 'count should equal 4 count=countTheCharacters(str,"t") 'count should equal 3 最直接的方法是简单地遍历string中的字符：
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较短的方法是使用LINQ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
这是简单的方法
text="the little red hen" count = text.Split("e").Length -1 ' Equals 4 count = text.Split("t").Length -1 ' Equals 3
你可以试试这个
Dim occurCount As Integer = Len(testStr) - Len(testStr.Replace(testCharStr, ""))
这是一个简单的版本。
text.count(function(x) x = "a")
以上将给你在string中的数字。 如果你想忽略大小写：
text.count(function(x) Ucase(x) = "A")
或者如果你只是想数字：
text.count(function(x) Char.IsLetter(x) = True)
试一试！
或（在VB.NET中）：
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
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())
谢谢， @guffa 。 在一行中，甚至在.NET中的更长的语句中执行它的function非常方便。 这个VB.NET例子计算了LineFeed字符的数量：
Dim j As Integer = MyString.Count(Function(c As Char) c = vbLf)
j返回MyString中的LineFeeds的数量。
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
当我find这个解决scheme时，我正在寻找稍微不同的东西，因为我想要计算的string长于一个字符，所以我提出了这个解决scheme：
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
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
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
代码用法：
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
代码用法：
Dim iCountTimes2 As Integer = "Can I call you now?".CountOccurrences("a")
我build议你这样做：
String.Replace("e", "").Count String.Replace("t", "").Count
你也可以使用.Split("e").Count - 1或者.Split("t").Count - 1 respetivelly，但是如果你有一个e或者at开头的String
使用正则expression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
eCount = str.Length - Replace(str, "e", "").Length tCount = str.Length - Replace(str, "t", "").Length
另一种可能性是与斯普利特合作：
Dim tmp() As String tmp = Split(Expression, Delimiter) Dim count As Integer = tmp.Length - 1
我find了最好的答案：P：
String.ToString.Count - String.ToString.Replace("e", "").Count String.ToString.Count - String.ToString.Replace("t", "").Count
'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
var charCount = "string with periods...".Count(x => '.' == x);
我使用以下function。 它不是最有效率的内存，但它很容易理解，支持多种比较方法，只有4行，速度快，大部分也在VBA中工作，不仅可以find单个字符而且可以查找任何string（我经常searchVbCrLf （一个或多个））。
唯一缺less的是从不同的“开始”开始search的能力
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
我喜欢的一件事是使用示例是紧凑的。
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shill我的inStB函数，而不是返回一个string的计数，它只会返回一个布尔值，如果searchstring存在。 我经常需要这个函数，这使得我的代码更清晰。
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
另一种可能性是使用正则expression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());
请把它转换成VB.NET。
我使用LINQ，解决scheme非常简单：
在C＃中的代码：
count = yourString.ToCharArray().Count(c => c == 'e');
函数中的代码：
public static int countTheCharacters(string str, char charToCount){ return str.ToCharArray().Count(c => c == charToCount); }
调用函数：
count = countTheCharacters(yourString, 'e');
使用：
Function fNbrStrInStr(strin As Variant, strToCount As String) fNbrStrInStr = UBound(Split(strin, strToCount)) - LBound(Split(strin, strToCount)) End Function
我使用strin作为变体的字符来处理非常长的文本。 拆分可以根据用户设置从零开始或基于一开始，并且减去它可以确保正确的计数。
我没有包含一个testingstrcount比strin更长的代码简洁。
什么巨大的代码如此简单：
在C＃中，创build一个扩展方法并使用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。
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
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
这是解决OP问题的直接代码：
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，解决OP的问题是一个方便的function：
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
使用该function的示例：
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
