如何找到字符串中子字符串的出現次數vb.net

Question

我有一個字符串（例如："Hello there. My name is John. I work very hard. Hello there!"），我試圖找到字符串"hello there"的出現次數。到目前爲止，這是我的代碼有：

Dim input as String = "Hello there. My name is John. I work very hard. Hello there!" 
Dim phrase as String = "hello there" 
Dim Occurrences As Integer = 0 

If input.toLower.Contains(phrase) = True Then 
    Occurrences = input.Split(phrase).Length  
    'REM: Do stuff 
End If 

不幸的是，這行代碼，似乎做的每一次拆分字符串它看到的phrase的第一個字母，在這種情況下，h。所以，而不是我希望的結果Occurrences = 2，我實際上得到一個更大的數字。我知道計算一個字符串中分割的次數是一個可怕的方式去做這件事，即使我確實得到了正確的答案，所以有人可以幫助我並提供一些幫助嗎？

Answer 1

您可以創建一個Do Until循環，停止一旦一個整數變量等於你正在檢查的字符串的長度。如果該短語存在，則增加您的出現次數，並將短語的長度加上發現它的位置添加到遊標變量中。如果無法找到該短語，則完成搜索（不再有結果），因此將其設置爲目標字符串的長度。要不止一次計算相同的出現次數，只需從光標檢查循環（strCheckThisString）中目標字符串的長度。

Dim input As String = "hello there. this is a test. hello there hello there!" 
    Dim phrase As String = "hello there" 
    Dim Occurrences As Integer = 0 

    Dim intCursor As Integer = 0 
    Do Until intCursor >= input.Length 

     Dim strCheckThisString As String = Mid(LCase(input), intCursor + 1, (Len(input) - intCursor)) 

     Dim intPlaceOfPhrase As Integer = InStr(strCheckThisString, phrase) 
     If intPlaceOfPhrase > 0 Then 

      Occurrences += 1 
      intCursor += (intPlaceOfPhrase + Len(phrase) - 1) 

     Else 

      intCursor = input.Length 

     End If 

    Loop 

Answer 2

您只需將分割函數的輸入更改爲一個字符串數組，然後拖動StringSplitOptions即可。

試試這行代碼：

Occurrences = input.Split({phrase}, StringSplitOptions.None).Length 

我沒有檢查這一點，但我想你也必須考慮到一個事實，即出現會太高由於您正在使用您的字符串分割，而不是實際計算它是字符串中有多少次，所以我覺得Occurrences = Occurrences - 1

希望這有助於

Answer 3

另一個想法：

Dim input As String = "Hello there. My name is John. I work very hard. Hello there!" 
Dim phrase As String = "Hello there" 
Dim Occurrences As Integer = (input.Length - input.Replace(phrase, String.Empty).Length)/phrase.Length 

你只需要確保phrase.Length > 0。

Answer 4

我不知道這是否更明顯？ 從longString開始檢查phrase中的數字字符的下一個字符，如果沒有找到phrase從第二個字符開始查找等。如果發現從當前位置開始agin加上phrase中的字符數和遞增值occurences

Module Module1 
Sub Main() 

    Dim longString As String = "Hello there. My name is John. I work very hard. Hello there! Hello therehello there" 

    Dim phrase As String = "hello There" 


    Dim occurences As Integer = 0 
    Dim n As Integer = 0 

    Do Until n >= longString.Length - (phrase.Length - 1) 
     If longString.ToLower.Substring(n, phrase.Length).Contains(phrase.ToLower) Then 
      occurences += 1 
      n = n + (phrase.Length - 1) 
     End If 
     n += 1 
    Loop 
    Console.WriteLine(occurences) 


End Sub 
End Module 

Answer 5

您可以使用IndexOf創建一個遞歸函數。傳遞要搜索的字符串和要查找的字符串，每個遞歸會增加一個計數器，並將StartIndex設置爲最後找到的索引+1，直到找不到搜索字符串。功能需要的可選參數起始位置，計數器按引用傳遞：

Function InStrCount(ByVal SourceString As String, _ 
        ByVal SearchString As String, _ 
        Optional ByRef StartPos As Integer = 0, _ 
        Optional ByRef Count As Integer = 0) As Integer 
    If SourceString.IndexOf(SearchString, StartPos) > -1 Then 
     Count += 1 
     InStrCount(SourceString, _ 
        SearchString, _ 
        SourceString.IndexOf(SearchString, StartPos) + 1, _ 
        Count) 
    End If 
    Return Count 
End Function 

呼叫傳入字符串搜索和字符串來定位和可選功能，開始位置：

Dim input As String = "Hello there. My name is John. I work very hard. Hello there!" 
Dim phrase As String = "hello there" 
Dim Occurrences As Integer 

Occurrances = InStrCount(input.ToLower, phrase.ToLower) 

注意使用。 ToLower，用於在比較中忽略大小寫。如果您希望比較是特定案例，請不要包含此指令。

Answer 6

做到這一點的最好辦法是這樣的：

Public Function countString(ByVal inputString As String, ByVal stringToBeSearchedInsideTheInputString as String) As Integer 
    Return System.Text.RegularExpressions.Regex.Split(inputString, stringToBeSearchedInsideTheInputString).Length -1 

End Function 

Answer 7

看你原來的嘗試，我發現，這應該做的伎倆是「拆分」創建一個數組。 紀錄= input.split（短語）.ubound

這是大小寫敏感的，所以你的情況應了那句輸入

Answer 8

我用等於「你好」，因爲沒有「你好」這在VBScript中，您可以在同一轉換成VB.net以及

Dim str, strToFind 
str = "sdfsdf:sdsdgs::" 
strToFind = ":" 

MsgBox GetNoOfOccurranceOf(strToFind, str) 

Function GetNoOfOccurranceOf(ByVal subStringToFind As String, ByVal strReference As String) 
    Dim iTotalLength, newString, iTotalOccCount 
    iTotalLength = Len(strReference) 
    newString = Replace(strReference, subStringToFind, "") 
    iTotalOccCount = iTotalLength - Len(newString) 
    GetNoOfOccurranceOf = iTotalOccCount 
End Function 

Answer 9

我知道這個線程是真的老了，但我得到了另一種解決方案也：

Function countOccurencesOf(needle As String, s As String) 
    Dim count As Integer = 0 
    For i As Integer = 0 to s.Length - 1 
     If s.Substring(i).Startswith(needle) Then 
      count = count + 1 
     End If 
    Next 
    Return count 
End Function 

Answer 10

str="Thisissumlivinginsumgjhvgsum in the sum bcoz sum ot ih sum" 
b= LCase(str) 
array1=Split(b,"sum") 
l=Ubound(array1) 
msgbox l 

輸出給你的號碼。在另一個字符串中出現的字符串。基於InStr(i, str, substr)功能

Answer 11

還有一種溶液（搜索在strsubstr從i位置，more info about InStr()開始）：

Function findOccurancesCount(baseString, subString) 
    occurancesCount = 0 
    i = 1 
    Do 
     foundPosition = InStr(i, baseString, subString) 'searching from i position 
     If foundPosition > 0 Then      'substring is found at foundPosition index 
      occurancesCount = occurancesCount + 1  'count this occurance 
      i = foundPosition + 1      'searching from i+1 on the next cycle 
     End If 
    Loop While foundPosition <> 0 
    findOccurancesCount = occurancesCount 
End Function 

一旦沒有找到字符串（InStr返回0，代替在找到的子串位置基本字符串），搜索結束並返回發生次數。