因數分解 - 副程式、函數、字串應用綜合演練版

'因數分解 - 副程式、函數、字串應用綜合演練版
Public Class Form1
    Dim bqn
    Dim a(20)
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim str2 = ""
        ' Dim qn = 720
        For qn = 1 To 50
            bqn = qn
            factorize(qn)
            str2 = str2 & toexpType(a) & vbNewLine
        Next
        MsgBox(str2)
        End
    End Sub

    Sub factorize(ByVal qn)
        ReDim a(20)
        Dim j = 0
        For k = 2 To qn
            While qn Mod k = 0
                qn = qn / k
                a(j) = k
                j = j + 1
            End While
        Next
        j = j - 1
        ReDim Preserve a(j)
    End Sub

    Function toexpType(ByVal a) As String
        Dim str1 = ""
        Dim p = 0
        Dim n = 1
        For i = 0 To a.Length - 1
            Dim c = a(i)
            If c <> p Then
                If str1 = "" Then
                    str1 = str1 & c & "^"
                Else
                    str1 = str1 & n & "*" & c & "^"
                End If
                n = 1
            Else
                n = n + 1
            End If
            p = c
        Next
        str1 = str1 & n
        str1 = Replace(str1, "^1", "")
        str1 = bqn & "=" & str1
        Return str1
    End Function
End Class