遞迴問題

Private Sub Command1_Click() 
Dim a As String 

a = Trim(InputBox("請輸入字串", , "123")) 
If a = "" Then Exit Sub 
ReDim c(1 To Len(a)) As Boolean 
cal a, "", c 
End SubSub cal(a As String, s As String, c() As Boolean) 
If Len(s) = Len(a) Then Print s: Exit Sub 
Dim i As Integer, tmp() As Boolean 
For i = 1 To Len(a) 
　　If Not c(i) Then 
　　　　tmp = c: tmp(i) = True 
　　　　cal a, s & Mid(a, i, 1), tmp 
　　End If 
Next 
End Sub

Hanoi Tower的解答網上有很多

解答

先要了解遞迴的規則

再去推算程式碼比較好理解