Private Sub Command1_Click()
s = Label1.Caption
c = ""
n = Len(s)
v = 0
r = 0
For i = 1 To n
If i <> 1 Then
Print "出去一个" & Mid(c, i - 1, 1)
c = Mid(c, i)
Print " 余下" & c
End If
Do While ((r + 1 <= n) And (InStr(c, Mid(s, r + 1, 1)) = 0))
Print "进来一个:" & Mid(s, r + 1, 1)
c = c & Mid(s, r + 1, 1)
Print "状态是:" & c
r = r + 1
Loop
If v <= r + 1 - i Then v = r + 1 - i
Next
Print v
End Sub