147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369147852369*36985214=5465465465465465465465465465465465465465465465465465465465465465465465465465465465465468351513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317513340317507871966有487位，用时0.5390625秒（末尾数字是与实际相同的，最高位咋又多了好多位？）

看看这样不行，无法调整了，把一位一组的程序再优化一下吧。

999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999（270位）*9=88888888888888888888888888888888888888888888888888888888888888999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999991有332位，用时0.5秒（不对了，多了很多8字，应该是271位）

修改了一下程序，这回可能对了，程序速度和模仿手工计算的相似，还能提高，希望老师能优化一下程序，前面的一位一组是对的，速度太慢能否优化？这个待优化的快速程序代码如下：

Private Sub Command1_Click()
  Dim xr() As String, a As String
  a = Trim(Text1)
  b = Trim(Text3)
  ts = Timer
  x = Len(a) \ 4: Y = Len(b) \ 4
  If Val(4 * x) = Len(a) Then
  a = a
  ElseIf Val(4 * Y) = Len(b) Then
  b = b
  Else
  a = String(Val(x * 4 + 4 - Len(a)), "0") & a
  b = String(Val(Y * 4 + 4 - Len(b)), "0") & b
  x = x + 1: Y = Y + 1
  End If
  
  
  sb1 = x + Y
  sb2 = Log(sb1) / Log(2)
  If InStr(sb2, ".") = 0 Then
  sb2 = sb2
  Else
  sb2 = Int(sb2) + 1
  End If
  sb = 2 ^ sb2
  Print sb
  

  a = String(Val(sb) * 4 - Len(a), "0") & a
  b = String(Val(sb) * 4 - Len(b), "0") & b
  a = dxcx0(Trim(a), Val(sb)): b = dxcx0(Trim(b), Val(sb))
  Print a
  ReDim xr(0 To (Len(a) - 4) \ 4): ReDim yr(0 To (Len(b) - 4) \ 4): ReDim zr(0 To (Len(b) - 4) \ 4)
  If Len(a) = 4 Then
  xr(0) = a: yr(0) = b
  Else
  For i1 = 0 To (Len(a) - 4) \ 4
  xr(i1) = Mid(a, (i1 + 1) * 4 - 3, 4)
  yr(i1) = Mid(b, (i1 + 1) * 4 - 3, 4)

     Next
     End If
  
  Dim xi(): Dim yi(): Dim zi()
  n = Len(a) \ 4 '求数组大小，其值必须是2的幂
m = 0
  l = 2
  pi = 3.14159265358979
  Do
  l = l + l
  m = m + 1
  Loop Until l > n
  n = l / 2
  ReDim xi(n - 1): ReDim yi(n - 1): ReDim zi(n - 1)

  l = 1
  Do
    le = 2 ^ l
    le1 = le / 2
    wr = 1
    wi = 0
    If l = 1 Then
    t = 0
    Else
    t = pi / le1
    End If
    w1r = Cos(t)
    w1i = -Sin(t)
    r = 0
  Do
    p = r
    Do
     q = p + le1
     
     tr = xr(q) * wr - xi(q) * wi
     ti = xr(q) * wi + xi(q) * wr
     tr1 = yr(q) * wr - yi(q) * wi
     ti1 = yr(q) * wi + yi(q) * wr
     
     
     xr(q) = xr(p) - tr
     xi(q) = xi(p) - ti
     xr(p) = xr(p) + tr
     xi(p) = xi(p) + ti
     
       yr(q) = yr(p) - tr1
      yi(q) = yi(p) - ti1
      yr(p) = yr(p) + tr1
      yi(p) = yi(p) + ti1
     xr(p) = Format(Val(xr(p)), "0.000000"): xi(p) = Format(Val(xi(p)), "0.000000")
     yr(p) = Format(Val(yr(p)), "0.000000"): yi(p) = Format(Val(yi(p)), "0.000000")
     Print xr(p), xr(q)
      p = p + le
  Loop Until p > n - 1


  wr2 = wr * w1r - wi * w1i
  wi2 = wr * w1i + wi * w1r
  wr = wr2
  wi = wi2
  r = r + 1
  Loop Until r > le1 - 1
  l = l + 1
  Loop Until l > m

  For I = 0 To n - 1 '仅输出模
   zr(I) = xr(I) * yr(I) - xi(I) * yi(I): zi(I) = xr(I) * yi(I) + xi(I) * yr(I)
      zr(I) = Format(Val(zr(I)), "0.000000"): zi(I) = Format(Val(zi(I)), "0.000000")

      s = s & "/" & zr(I)
      s1 = s1 & "/" & zi(I)
      Next
     s2 = nifft(dxcx1(Trim(s)), dxcx1(Trim(s1)), Trim(sb1))
     
      Text2 = s2 & "有" & Len(s2) & "位，用时" & Timer - ts & "秒"
  End Sub

  Private Sub Command2_Click()
  Text1 = ""
  Text2 = ""
  Text3 = ""
  Form1.Cls
  End Sub

Private Function qdqd0(sa As String) As String
  a = sa
  Do While Left(a, 1) = "0"
  a = Mid(a, 2)
  Loop
  If a = "" Then
  a = 0
  Else
  a = a
  End If
  qdqd0 = a
  End Function


  Private Function nifft(sa As String, sb As String, sb1 As String) As String
  
  Dim xi(): Dim yi(): Dim zi()
  Dim xr(), yr()
  Dim zr() As String
  
  s2 = Split(sa, "/")
  s3 = Split(sb, "/")
      J = UBound(s2)
      n = J
     For k = 1 To J
         n1 = n1 + 1
          ReDim Preserve xr(0 To n1 - 1)
          ReDim Preserve yr(0 To n1 - 1)
         xr(n1 - 1) = s2(n1): yr(n1 - 1) = s3(n1)
         xr(n1 - 1) = Format(Val(xr(n1 - 1)), "0.000000"): yr(n1 - 1) = Format(Val(yr(n1 - 1)), "0.000000")

       Next
     

  ReDim zr(0 To J - 1)

  m = 0
  l = 2
  pi = 3.14159265358979
  Do
  l = l + l
  m = m + 1
  Loop Until l > n
  n = l / 2
  ReDim xi(n - 1): ReDim yi(n - 1): ReDim zi(n - 1)

  l = 1
  Do
    le = 2 ^ l
    le1 = le / 2
    wr = 1
    wi = 0
    If l = 1 Then
    t = 0
    Else
    t = -1 * pi / le1
    End If
    w1r = Cos(t)
    w1i = -Sin(t)
    r = 0
  Do
    p = r
    Do
     q = p + le1
     
     tr = xr(q) * wr - xi(q) * wi
     ti = xr(q) * wi + xi(q) * wr
     tr1 = yr(q) * wr - yi(q) * wi
     ti1 = yr(q) * wi + yi(q) * wr
     
     
     xr(q) = xr(p) - tr
     xi(q) = xi(p) - ti
     xr(p) = xr(p) + tr
     xi(p) = xi(p) + ti
     
       yr(q) = yr(p) - tr1
      yi(q) = yi(p) - ti1
      yr(p) = yr(p) + tr1
      yi(p) = yi(p) + ti1
     xr(p) = Format(Val(xr(p)), "0.000000"): xi(p) = Format(Val(xi(p)), "0.000000")
     yr(p) = Format(Val(yr(p)), "0.000000"): yi(p) = Format(Val(yi(p)), "0.000000")
      p = p + le
  Loop Until p > n - 1


  wr2 = wr * w1r - wi * w1i
  wi2 = wr * w1i + wi * w1r
  wr = wr2
  wi = wi2
  r = r + 1
  Loop Until r > le1 - 1
  l = l + 1
  Loop Until l > m

  For I = 0 To n - 1 '仅输出模
zr(I) = (xr(I) - yi(I)) / n
      zr(I) = Format(Val(zr(I) + 0.5), "0.000000")
     If InStr(zr(I), ".") = 0 Then
     s1 = zr(I)
     Else
     s1 = Left(zr(I), InStr(zr(I), ".") - 1)
      End If
      s = "/" & s1 & s
      zr(I) = s1
      Next
      For i1 = 1 To Val(J - sb1 + 1)
      zr(sb1 + i1 - 2) = 0
      Next
      
     
     
      For i1 = 0 To n - 1
      If zr(i1) < 0 Then
      zr(i1) = "00000000"
      Else
      zr(i1) = zr(i1)
      End If
      s5 = s5 & "/" & zr(i1)
      
      If i1 = 0 Then
      If Len(zr(i1)) < 4 Then
      zr(i1) = String(4 - Len(zr(i1)), "0") & zr(i1)
      Else
      zr(i1) = zr(i1)
      End If
      s6 = Val(Left(zr(i1), Len(zr(i1)) - 4))
      If Len(s6) < 4 Then
      s6 = String(4 - Len(s6), "0") & s6
      Else
      s6 = s6
      End If
      s8 = Right(zr(i1), 4)
      ElseIf Val(zr(i1)) >= 0 Then
      s7 = MPC1(Trim(zr(i1)), Trim(s6))
      s10 = Right(s7, 4)
      s11 = s10 & s11
      If Len(s7) < 4 Then
      s7 = String(4 - Len(s7), "0") & s7
      ElseIf Len(s7) = 4 Then
      s6 = "00000000"
      Else
      s7 = s7
      s6 = Val(Left(s7, Len(s7) - 4))
      End If
      Else
      s6 = s6
      End If
     
      Next
      s9 = s6 & s11 & s8
     
  nifft = qdqd0(Trim(s9))

  End Function

  Private Function dxcx0(sa As String, sb As String) As String

  Dim x_() As String, a As String
    a = Trim(sa)
    ReDim x_(1 To sb)
    For i1 = 1 To sb
    x_(i1) = Mid(a, (sb - i1 + 1) * 4 - 3, 4)
    If Len(x_(i1)) < 4 Then
    x_(i1) = String(4 - Len(x_(i1)), "0") & x_(i1)
    Else
    x_(i1) = x_(i1)
    End If
   
      Next
    Dim n As Integer, I As Long, J As Long, mn As Long, lh As Long, t As Double, k As Long
    '位序倒置
n = sb '求数组大小，其值必须是2的幂
lh = n / 2
    J = n / 2
    For I = 1 To n - 2


    Debug.Print I, J
    k = lh '下面是向右进位算法
Do
    If k > J Then Exit Do '高位是1吗
J = J - k '是的，高位置0
    k = k / 2 '准备次高位的权
Loop Until k = 0 '次高位的权若非0，则检查新的次高位
J = J + k '非则若最高位是0，则置1
    s = s & x_(J + 1)
    Next
    dxcx0 = x_(1) & x_(1 + sb / 2) & s
   
   

  End Function

  Private Function dxcx1(sa As String) As String

  Dim x_() As Double, a As String
    a = Trim(sa)
     

  s2 = Split(sa, "/")
  s3 = Split(sb, "/")
      J = UBound(s2)
      sb = J
     
       ReDim x_(1 To sb)
     For k = 1 To J
         n1 = n1 + 1
          ReDim Preserve x_(1 To n1)
        
         x_(n1) = Format(Val(s2(n1)), "0.000000")
       Next
    Dim n As Integer, I As Long, mn As Long, lh As Long, t As Double
    '位序倒置
n = sb '求数组大小，其值必须是2的幂
lh = n / 2
    J = n / 2
    For I = 1 To n - 2


    Debug.Print I, J
    k = lh '下面是向右进位算法
Do
    If k > J Then Exit Do '高位是1吗
J = J - k '是的，高位置0
    k = k / 2 '准备次高位的权
Loop Until k = 0 '次高位的权若非0，则检查新的次高位
J = J + k '非则若最高位是0，则置1
x_(J + 1) = Format(Val(x_(J + 1)), "0.000000")
    s = s & "/" & x_(J + 1)
    Next
    x_(1) = Format(Val(x_(1)), "0.000000"): x_(1 + sb / 2) = Format(Val(x_(1 + sb / 2)), "0.000000")
    dxcx1 = "/" & x_(1) & "/" & x_(1 + sb / 2) & s
   
    End Function

Public Function MPC1(D1 As String, D2 As String) As String 'jiafa
Dim x, Y '两数长度

If Len(D1) >= Len(D2) Then
D4 = String(Len(D1) - Len(D2), "0") & D2
d3 = D1
Else
D4 = D2
d3 = String(Len(D2) - Len(D1), "0") & D1
End If
x = Len(d3): Y = Len(D4)
Dim a() As Integer, B1() As Integer, C1() As Integer, E1() As Integer
ReDim a(1 To x)
ReDim B1(1 To Y)
ReDim C1(1 To x)
ReDim E1(1 To x)
Dim I, J, C2, CJ, JW
For J = Y To 1 Step -1 'D2
JW = 0 '进位清0
B1(J) = Mid$(D4, J, 1) '每位数
For I = x To 1 Step -1  'D1
   a(I) = Mid$(d3, I, 1) '每位数
   C1(I) = a(I) + B1(I) + JW '计算jia
   JW = C1(I) \ 10
   E1(I) = C1(I) Mod 10
  Next
  Next
  For r = 1 To x
  If JW = 0 Then
  MPC1 = MPC1 & E1(r)
  Else
  jc = jc & E1(r)
  MPC1 = JW & jc
  End If
  Next
  
End Function

[此贴子已经被作者于2021-3-20 10:24编辑过]

999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999（270位）*9=8999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999991有271位，用时0.8242188秒（哈哈哈这回可能对了）

111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111*111111111=12345678999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999987654321有221位，用时0.3984375秒（结果是对的，速度提高了一点，可能还有提升空间，希望帮助优化，谢谢各位老师！）

优化的程序，一位一组的，没有完成速度提高不明显，暂时发一下：（有空在接着弄吧，有提升空间）

Dim l As Long, le As Long, le1 As Long, n As Long, r As Long, p As Long, q As Long, m As Byte
  Dim wr As Double, w1 As Double, wlr As Double, wl1 As Double, tr As Double, t1 As Double
  Dim pi As Double, t As Double, tr1 As Double

Private Sub Command1_Click()
  Dim xr() As Double, a As String
  a = Trim(Text1)
  b = Trim(Text3)
  ts = Timer
  
  Text2 = js & "有" & Len(js) & "位，用时" & Timer - ts & "秒"
  sb1 = Len(a) + Len(b)
  sb2 = Log(sb1) / Log(2)
  If InStr(sb2, ".") = 0 Then
  sb2 = sb2
  Else
  sb2 = Int(sb2) + 1
  End If
  sb = 2 ^ sb2
  Print sb
  If Len(a) = Len(b) And 2 ^ (Int(Log(Len(a)) / Log(2))) = Len(a) Then
    a = String(Val(sb) - Len(a), "0") & a
  b = String(Val(sb) - Len(b), "0") & b
  ax = a: bx = b
  Else

  a = String(Val(sb) - Len(a), "0") & a
  b = String(Val(sb) - Len(b), "0") & b
  ax = a: bx = b
  End If
  Dim y_() As Double, x_() As Double
  ReDim x_(1 To sb): ReDim y_(1 To sb)
    For i1 = 1 To sb
    x_(i1) = Mid(ax, sb - i1 + 1, 1): y_(i1) = Mid(bx, sb - i1 + 1, 1)
      Next
    Dim n As Integer, I As Long, J As Long, mn As Long, lh As Long, t As Double, k As Long
    '位序倒置
n = sb '求数组大小，其值必须是2的幂
lh = n / 2
    J = n / 2
    For I = 1 To n - 2


    Debug.Print I, J
    k = lh '下面是向右进位算法
Do
    If k > J Then Exit Do '高位是1吗
J = J - k '是的，高位置0
    k = k / 2 '准备次高位的权
Loop Until k = 0 '次高位的权若非0，则检查新的次高位
J = J + k '非则若最高位是0，则置1
    s = s & x_(J + 1)
    s1 = s1 & y_(J + 1)
    Next
    a = x_(1) & x_(1 + sb / 2) & s
    b = y_(1) & y_(1 + sb / 2) & s1
  
  ReDim xr(0 To Len(a) - 1): ReDim yr(0 To Len(b) - 1): ReDim zr(0 To Len(b) - 1)
  For i1 = 0 To Len(a) - 1
  xr(i1) = Mid(a, i1 + 1, 1)
  yr(i1) = Mid(b, i1 + 1, 1)

     Next
  
  Dim xi(): Dim yi(): Dim zi()
  n = Len(a) '求数组大小，其值必须是2的幂
m = 0
  l = 2
  pi = 3.14159265358979
  Do
  l = l + l
  m = m + 1
  Loop Until l > n
  n = l / 2
  ReDim xi(n - 1): ReDim yi(n - 1): ReDim zi(n - 1)

  l = 1
  Do
    le = 2 ^ l
    le1 = le / 2
    wr = 1
    wi = 0
    If l = 1 Then
    t = 0
    Else
    t = pi / le1
    End If
    w1r = Cos(t)
    w1i = -Sin(t)
    r = 0
  Do
    p = r
    Do
     q = p + le1
     
     tr = xr(q) * wr - xi(q) * wi
     ti = xr(q) * wi + xi(q) * wr
     tr1 = yr(q) * wr - yi(q) * wi
     ti1 = yr(q) * wi + yi(q) * wr
     
     
     xr(q) = xr(p) - tr
     xi(q) = xi(p) - ti
     xr(p) = xr(p) + tr
     xi(p) = xi(p) + ti
     
       yr(q) = yr(p) - tr1
      yi(q) = yi(p) - ti1
      yr(p) = yr(p) + tr1
      yi(p) = yi(p) + ti1
     
      p = p + le
  Loop Until p > n - 1


  wr2 = wr * w1r - wi * w1i
  wi2 = wr * w1i + wi * w1r
  wr = wr2
  wi = wi2
  r = r + 1
  Loop Until r > le1 - 1
  l = l + 1
  Loop Until l > m

  For I = 0 To n - 1 '仅输出模
   zr(I) = xr(I) * yr(I) - xi(I) * yi(I): zi(I) = xr(I) * yi(I) + xi(I) * yr(I)
      

      's = s & "/" & zr(I)
      's1 = s1 & "/" & zi(I)
      Next
      
       J = sb
     
       ReDim x_(1 To sb): ReDim y_(1 To sb)
     For k = 1 To J
         n1 = n1 + 1
          ReDim Preserve x_(1 To n1)
        
         x_(n1) = zr(n1 - 1): y_(n1) = zi(n1 - 1)
       Next
   
    '位序倒置
n = sb '求数组大小，其值必须是2的幂
lh = n / 2
    J = n / 2
    For I = 1 To n - 2


    Debug.Print I, J
    k = lh '下面是向右进位算法
Do
    If k > J Then Exit Do '高位是1吗
J = J - k '是的，高位置0
    k = k / 2 '准备次高位的权
Loop Until k = 0 '次高位的权若非0，则检查新的次高位
J = J + k '非则若最高位是0，则置1
    js = js & "/" & x_(J + 1)
    js1 = js1 & "/" & y_(J + 1)
    Next
    sx1 = "/" & x_(1) & "/" & x_(1 + sb / 2) & js
    sy1 = "/" & y_(1) & "/" & y_(1 + sb / 2) & js1
   
   
   
   
   
      
      
     's2 = nifft(dxcx1(Trim(s)), dxcx1(Trim(s1)), Trim(sb1))
     s3 = nifft(Trim(sx1), Trim(sy1), Trim(sb1))
      Text2 = s3 & "有" & Len(s3) & "位，用时" & Timer - ts & "秒"
  End Sub

  Private Sub Command2_Click()
  Text1 = ""
  Text2 = ""
  Text3 = ""
  Form1.Cls
  End Sub

Private Function qdqd0(sa As String) As String
  a = sa
  Do While Left(a, 1) = "0"
  a = Mid(a, 2)
  Loop
  If a = "" Then
  a = 0
  Else
  a = a
  End If
  qdqd0 = a
  End Function

  Private Function nifft(sa As String, sb As String, sb1 As String) As String
  
  Dim xi(): Dim yi(): Dim zi()
  Dim xr(), yr(), zr()
  s2 = Split(sa, "/")
  s3 = Split(sb, "/")
      J = UBound(s2)
      n = J
     For k = 1 To J
         n1 = n1 + 1
          ReDim Preserve xr(0 To n1 - 1)
          ReDim Preserve yr(0 To n1 - 1)
         xr(n1 - 1) = s2(n1): yr(n1 - 1) = s3(n1)
       Next
     

  ReDim zr(0 To J - 1)

  m = 0
  l = 2
  pi = 3.14159265358979
  Do
  l = l + l
  m = m + 1
  Loop Until l > n
  n = l / 2
  ReDim xi(n - 1): ReDim yi(n - 1): ReDim zi(n - 1)

  l = 1
  Do
    le = 2 ^ l
    le1 = le / 2
    wr = 1
    wi = 0
    If l = 1 Then
    t = 0
    Else
    t = -1 * pi / le1
    End If
    w1r = Cos(t)
    w1i = -Sin(t)
    r = 0
  Do
    p = r
    Do
     q = p + le1
     
     tr = xr(q) * wr - xi(q) * wi
     ti = xr(q) * wi + xi(q) * wr
     tr1 = yr(q) * wr - yi(q) * wi
     ti1 = yr(q) * wi + yi(q) * wr
     
     
     xr(q) = xr(p) - tr
     xi(q) = xi(p) - ti
     xr(p) = xr(p) + tr
     xi(p) = xi(p) + ti
     
       yr(q) = yr(p) - tr1
      yi(q) = yi(p) - ti1
      yr(p) = yr(p) + tr1
      yi(p) = yi(p) + ti1
     
      p = p + le
  Loop Until p > n - 1


  wr2 = wr * w1r - wi * w1i
  wi2 = wr * w1i + wi * w1r
  wr = wr2
  wi = wi2
  r = r + 1
  Loop Until r > le1 - 1
  l = l + 1
  Loop Until l > m

  For I = 0 To n - 1 '仅输出模
zr(I) = (xr(I) - yi(I)) / n
      
     
      s1 = Int(Val(zr(I) + 0.5))
      s = "/" & s1 & s
      zr(I) = s1
      Next
      For i1 = 1 To Val(J - sb1 + 1)
      zr(sb1 + i1 - 2) = 0
      Next
      
     
     
      For i1 = 0 To n - 1
      If zr(i1) < 0 Then
      zr(i1) = 0
      Else
      zr(i1) = zr(i1)
      End If
      
      s5 = "/" & Int(zr(i1)) & s5
      If i1 = 0 Then
      s6 = Int(zr(i1)) \ 10
      s8 = Int(zr(i1)) Mod 10
      ElseIf Val(zr(i1)) >= 0 Then
      s7 = Int(zr(i1)) + Val(s6)
      s10 = Val(s7) Mod 10
      s11 = s10 & s11
      s6 = Val(s7) \ 10
      Else
      s6 = Val(s6)
      End If
     
      Next
      s9 = s6 & s11 & s8
     
  nifft = qdqd0(Trim(s9))

  End Function

  Private Function dxcx0(sa As String, sb As String) As String

  Dim x_() As Double, a As String
    a = Trim(sa)
    ReDim x_(1 To sb)
    For i1 = 1 To sb
    x_(i1) = Mid(a, sb - i1 + 1, 1)
      Next
    Dim n As Integer, I As Long, J As Long, mn As Long, lh As Long, t As Double, k As Long
    '位序倒置
n = sb '求数组大小，其值必须是2的幂
lh = n / 2
    J = n / 2
    For I = 1 To n - 2


    Debug.Print I, J
    k = lh '下面是向右进位算法
Do
    If k > J Then Exit Do '高位是1吗
J = J - k '是的，高位置0
    k = k / 2 '准备次高位的权
Loop Until k = 0 '次高位的权若非0，则检查新的次高位
J = J + k '非则若最高位是0，则置1
    s = s & x_(J + 1)
    Next
    dxcx0 = x_(1) & x_(1 + sb / 2) & s
   

  End Function

Public Function MbC(D1 As String, D2 As String) As String '乘法
Dim x, Y '两数长度
x = Len(D1): Y = Len(D2)
Dim a() As Integer
ReDim a(1 To x + Y, 1 To Y)
Dim I, J, C1, C2, CJ, JW
For J = Y To 1 Step -1 'D2
JW = 0 '进位清0
C2 = Mid$(D2, J, 1) '每位数
For I = x To 1 Step -1 'D1
  C1 = Mid$(D1, I, 1) '每位数
  CJ = C1 * C2 + JW '计算乘积
  c = I + J: r = Y + 1 - J
  a(c, r) = CJ Mod 10 '本位
  JW = CJ \ 10 '进位
Next
a(c - 1, r) = JW
Next
Dim b() As Integer
ReDim b(1 To x + Y)
JW = 0
For I = x + Y To 1 Step -1
Bit = JW
For J = 1 To Y
  Bit = Bit + a(I, J)
Next
b(I) = Bit Mod 10
JW = Bit \ 10
Next
If b(1) > 0 Then
MbC = MbC & b(1)
Else
MbC = MbC
End If
For I = 2 To x + Y
MbC = MbC & b(I)
Next
End Function

  Private Function dxcx1(sa As String) As String

  Dim x_() As Double, a As String
    a = Trim(sa)
     

  s2 = Split(sa, "/")
  s3 = Split(sb, "/")
      J = UBound(s2)
      sb = J
     
       ReDim x_(1 To sb)
     For k = 1 To J
         n1 = n1 + 1
          ReDim Preserve x_(1 To n1)
        
         x_(n1) = s2(n1)
       Next
    Dim n As Integer, I As Long, mn As Long, lh As Long, t As Double
    '位序倒置
n = sb '求数组大小，其值必须是2的幂
lh = n / 2
    J = n / 2
    For I = 1 To n - 2


    Debug.Print I, J
    k = lh '下面是向右进位算法
Do
    If k > J Then Exit Do '高位是1吗
J = J - k '是的，高位置0
    k = k / 2 '准备次高位的权
Loop Until k = 0 '次高位的权若非0，则检查新的次高位
J = J + k '非则若最高位是0，则置1
    s = s & "/" & x_(J + 1)
    Next
    dxcx1 = "/" & x_(1) & "/" & x_(1 + sb / 2) & s
   
    End Function

[此贴子已经被作者于2021-3-20 21:31编辑过]

这是模仿手工计算的程序结果，看上去比傅立叶变换的程序还快？结果如下：
51750801837147361345408953922231823615475578427966187002956389087112242842559611794590895524485015222232340190036677951157401229518412775512617768569186939216558814320044037671525512763073762127357272238470370174050144130962253437215369727381909754581075278888137687950749577751967083233227932391898438489520107788418593104216764745143648165875043861634459264809523254076330115365651752264033578829280651927862062277153553168278640509846511729608378923480331705134467105387853440058108864733429085916392927954109944314725590758950098556991513109760871599045355054258610189920009222629391227784118536578933067532162200768112408111142115021110731900107445187734955403922470144187293970602024056652942406064101184615113779243566842311336047149767396006622923831778833173731302325162741660053390002572456069410383734906953419854919650114722834689335022576764661864630532595250136417800041415827379233503655173380741283758557001102498493237113089198106283487003030225058520047964863929279622015825870972146222540614667928697270131499340362072956956518213266361286372027834000838185920579641835952404678850816456467012890793914108776148483471455515695596694573035435841962871983614397882366460940068418989292218104650923374259244879331938925143014431488635252724366437874702141802712286424754174951797598162531093933772708024046029028652425912112434874797404878317364682580259997737809632860143160557722236459697738869857870982308547756781808568834445404196611833859447257611721058384661943492980180884154939581533269700568975940675513953240040220315659784214936947443784598154082110443748171557676558299300252057475022409541083454882202785077569281268346332901357829843950754331120530978456454396022570647840977328115888711408099894489014427119253061839770890965114853246067272044090282103668762164047374624856119676063310166566519499552342907590495696658359542582469176737197423550084705962160477441546453931948920780829433665262356431973422034925001341330921812806939990688094288773216182971976433480031438271163051341645350474631300965486818841553843112688792803367397276204832936049162335586140151875524537720425345701193713093955432559579831822084761702059241698184717469616732582600658006352069963017377661059372648121969448644394344799369193952197519795756182552461838014896498816263546256621347748100920475049252091842372001283217811864786225692344297842649982716736752004086642881662614773154743879410328420184057019873899911520017723788801*
51750801837147361345408953922231823615475578427966187002956389087112242842559611794590895524485015222232340190036677951157401229518412775512617768569186939216558814320044037671525512763073762127357272238470370174050144130962253437215369727381909754581075278888137687950749577751967083233227932391898438489520107788418593104216764745143648165875043861634459264809523254076330115365651752264033578829280651927862062277153553168278640509846511729608378923480331705134467105387853440058108864733429085916392927954109944314725590758950098556991513109760871599045355054258610189920009222629391227784118536578933067532162200768112408111142115021110731900107445187734955403922470144187293970602024056652942406064101184615113779243566842311336047149767396006622923831778833173731302325162741660053390002572456069410383734906953419854919650114722834689335022576764661864630532595250136417800041415827379233503655173380741283758557001102498493237113089198106283487003030225058520047964863929279622015825870972146222540614667928697270131499340362072956956518213266361286372027834000838185920579641835952404678850816456467012890793914108776148483471455515695596694573035435841962871983614397882366460940068418989292218104650923374259244879331938925143014431488635252724366437874702141802712286424754174951797598162531093933772708024046029028652425912112434874797404878317364682580259997737809632860143160557722236459697738869857870982308547756781808568834445404196611833859447257611721058384661943492980180884154939581533269700568975940675513953240040220315659784214936947443784598154082110443748171557676558299300252057475022409541083454882202785077569281268346332901357829843950754331120530978456454396022570647840977328115888711408099894489014427119253061839770890965114853246067272044090282103668762164047374624856119676063310166566519499552342907590495696658359542582469176737197423550084705962160477441546453931948920780829433665262356431973422034925001341330921812806939990688094288773216182971976433480031438271163051341645350474631300965486818841553843112688792803367397276204832936049162335586140151875524537720425345701193713093955432559579831822084761702059241698184717469616732582600658006352069963017377661059372648121969448644394344799369193952197519795756182552461838014896498816263546256621347748100920475049252091842372001283217811864786225692344297842649982716736752004086642881662614773154743879410328420184057019873899911520017723788801=
2678145490787694710138406683675886762424440548647327525594133873038347266950777818028529804877891353347244255046176220880989519574806598935727647635506939520211209794328712328126947740602255036264392628020291100698432900022333877728824270241063030019536831205264726059774673235680796770108334187808344470141093691232926021244583649747591446066921535333854157441330339217364515328375889937313870826987520723914810358707312468857074455945610038118763873992681688857200178452843740327143990247797893489008808544535536081089994800692174759199578596435124153437689121057209523619989593900355037400039597165241729693472001589594642879166693443994939359639600558001937547209387175085119128575833396037478944824322315197771750730768383267287661855880237549141571520374996029107650341071074081501632143441365461865431362023790463469688071768208320226561675630348708531708110373889241713511809029065048200924851629507265095151843687852114948736130517024578482059771284515915597919026074110811882700307150650858080695566672584075215926450360584738705106755945308199980660478183563586945902705730231409948938478910176292179410952310592864745025373902249844607078729230098512959498522851990040833671698873183076996740726479481352429756295966452788332789259316653805673821716832204368483794501474641036177256005810416507649770210480747056764697918800240201155395628561684853684747063434500664449114760179367086926249813006056735202795763742271472136500817313178050955623517148960973128433455798444839070215800699075256371341531892841721456473301085595261371522078416420399702683504171019191363372883472415693921509069484448792009627325245658854979159002549542769741504596589556474585723101403486046952706847309188488390899096649210853675228464611999630360164703837131620319658277117300208326944026347808645954842782309633205645471959842390075986572806483755223497552549948718545978420793425036666212191832327909389117021539426917904222971515424022606157676379417252939026404363841301595348953340657745965591468370831371449860774296757556463049237248472613472436666799615694672489600751763956185893123579218797539971253828850163437053164723845196089466298000486042246621634263064752906475198879616484926366053597071510886820878425907736453843197228282179943365206039514850477377542684361730162273246709577442085159313947668552462343596819299335060863266863059421286080919061657175757802930378698062290163092494909661982639303946271889619023417245433500782685534406291391527022657608608130680134939380126048353657648559735671562230714451258764762350451448379438849319710473631625533527602085050858633346936315115309333355986556546113134787213610042970405680162084678021281774169131725296977361816657904233850711837826724976507876061043779177845550646612327663283839673950405472039432309339110648301347672597370034346896334064135099613033528785924976781865447506814375627647103020761819104412269362847848884053177378762432543285984193091289854949394023586451139393716370633759317698908834326333339634557238526607966375935960004339535161203546369910853171524516945554862019134684985868547068709986010719120259421723270478586992153989283736650948010894951434857207445141886625290777550599700738909777829412358941157674866550887608199469723859806486384262574182811908513849905040209776132986875560077482527819093584150609347560543627976011009349905362597935257895287412087233810106693141683912683308201407373637490835862452911394718399632093441745957478079754723679119343225931665785380948807114301164623717144211285944154289093317610519159281033583963015810556464180819928345256832572962092994993950655913067768151113345566231088759030148164710287289335782462899525700500822021472132532771242198844498579102733028256523810973405350508253183399668290339844052874956694050028526577775764032598023622192221226501334606994447870277619118208162133562541678250491647671042612088902952091163094215645902682086024337098910110924115381788866213335441814530141911754446270296630426675020592640816713810936850961517475097707179713115856513919631998747192606018612535436009162735908155778165736923393260822217415131632296810207091918499370220533980666393617256227781299273913099896641458499949922475383775878771011361417556799406151773618626138749998464514570482965286184387350245762317271666329142667987131139265167425606863654107927682419958167046956962340419295394058625063862272314570914511355913547470055072878835349142049813368019960713974852351833144227544851625677753419141348585495260230041111323576432417502998832485027071744397105338790364666312325483218209150368759120749671419554589928540715813531144241705501211397506662448276056294585639532800634727428900861538486753011006379264618338782036690340859441153926551954112364946638768223012718907190897165613382555036872673785444132692292217184974818914501886689736449912131900762592363447945036085692999163815947845753538999001633767986447907729462453017601有4888位，用时3.929688秒

111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111*111111111=12345678999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999987654321有221位，用时0.2578125秒（经过优化速度略有提高，可能还有提升空间）

111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111*111111111=12345678999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999987654321有221位，用时0.0859375秒（这个快，是4位一组的程序，还有可以优化的空间）

999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999*9=8999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999991有271位，用时0.28125秒（这个是对的，速度还可以，还有提升空间，是4位一组的程序）