[2008] How to check if all the chars in a string are different from each other?

[Lasering]

Hi!!

How can I check if all the chars in a string are different from each other? In other words how can I check if there are repeated chars in a string?

Thks a lot!

[.paul.]

try this:

MsgBox("string contains duplicate characters = " & checkString("astringa"))

Private Function checkString(ByVal str As String) As Boolean
        
     For x As Integer = 0 To str.Length - 1
          If x > 0 Then
             If CStr(str.Substring(0, x) & str.Substring(x + 1, str.Length - (x + 1))).Contains(str.Substring(x, 1)) Then
                Return True
             End If
          Else
             If str.Substring(x + 1, str.Length - (x + 1)).Contains(str.Substring(x, 1)) Then
                 Return True
             End If
          End If
     Next
     Return False
 
End Function

[VBDT]

Well, the question is a little bit vague. You don’t specify the casing. If the method should be case sensitive, than here is the method:

'Case sensitive
Private Function ContainsDuplicate(ByRef str As String) As Boolean
    For i As Integer = 0 To str.Length - 1
        If str.Substring(0, i).Contains(str.Substring(i, 1)) Then
            Return True
        End If
    Next
    Return False
End Function

If it is not spouse to be case sensitive, than add ToLower method after str and leave the rest the same, here is an example:

'None case sensitive
Private Function ContainsDuplicate(ByRef str As String) As Boolean
    For i As Integer = 0 To str.Length - 1
        If str.ToLower.Substring(0, i).Contains(str.ToLower.Substring(i, 1)) Then
            Return True
        End If
    Next
    Return False
End Function

[jmcilhinney]

For index As Integer = 0 To myString.Length - 1
    If myString.LastIndexOf(myString(index)) <> index Then
        'There is a least one more occurrence in the string of the character at the current index.
    End If
Next