代码如下，加了大整数加法程序，因为最后变换得到的数组会超过15位的，有时候可能是有3*8=24位，所以8位一组不好，最好4位，最多弄5位的可能是就可以了，有可能可以省去大数加法程序。明天试试吧，今天的程序如下：

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 String, a As String
  a = Trim(Text1)
  b = Trim(Text3)
  ts = Timer
  x = Len(a) \ 8: Y = Len(b) \ 8
  If Val(8 * x) = Len(a) Then
  a = a
  ElseIf Val(8 * Y) = Len(b) Then
  b = b
  Else
  a = String(Val(x * 8 + 8 - Len(a)), "0") & a
  b = String(Val(Y * 8 + 8 - 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) * 8 - Len(a), "0") & a
  b = String(Val(sb) * 8 - Len(b), "0") & b
  a = dxcx0(Trim(a), Val(sb)): b = dxcx0(Trim(b), Val(sb))
  Print a
  ReDim xr(0 To (Len(a) - 8) \ 8): ReDim yr(0 To (Len(b) - 8) \ 8): ReDim zr(0 To (Len(b) - 8) \ 8)
  If Len(a) = 8 Then
  xr(0) = a: yr(0) = b
  Else
  For i1 = 0 To (Len(a) - 8) \ 8
  xr(i1) = Mid(a, (i1 + 1) * 8 - 7, 8)
  yr(i1) = Mid(b, (i1 + 1) * 8 - 7, 8)

     Next
     End If
  
  Dim xi(): Dim yi(): Dim zi()
  n = Len(a) \ 8 '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)) < 8 Then
      zr(i1) = String(8 - Len(zr(i1)), "0") & zr(i1)
      Else
      zr(i1) = zr(i1)
      End If
      s6 = Val(Left(zr(i1), Len(zr(i1)) - 8))
      If Len(s6) < 8 Then
      s6 = String(8 - Len(s6), "0") & s6
      Else
      s6 = s6
      End If
      s8 = Right(zr(i1), 8)
      ElseIf Val(zr(i1)) >= 0 Then
      s7 = MPC1(Trim(zr(i1)), Trim(s6))
      s10 = Right(s7, 8)
      s11 = s10 & s11
      If Len(s7) < 8 Then
      s7 = String(8 - Len(s7), "0") & s7
      ElseIf Len(s7) = 8 Then
      s6 = "00000000"
      Else
      s7 = s7
      s6 = Val(Left(s7, Len(s7) - 8))
      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) * 8 - 7, 8)
    If Len(x_(i1)) < 8 Then
    x_(i1) = String(8 - 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

2678145490787694710138406683675886762424440548647327525594133873038347266950777818028529804877891353347244255046176220880989519574806598935727647635506939520211209794328712328126947740602255036264392628020291100698432900022333877728824270241063030019536831205264726059774673235680796770108334187808344470141093691232926021244583649747591446066921535333854157441330339217364515328375889937313870826987520723914810358707312468857074455945610038118763873992681688857200178452843740327143990247797893489008808544535536081089994800692174759199578596435124153437689121057209523619989593900355037400039597165241729693472001589594642879166693443994939359639600558001937547209387175085119128575833396037478944824322315197771750730768383267287661855880237549141571520374996029107650341071074081501632143441365461865431362023790463469688071768208320226561675630348708531708110373889241713511809029065048200924851629507265095151843687852114948736130517024578482059771284515915597919026074110811882700307150650858080695566672584075215926450360584738705106755945308199980660478183563586945902705730231409948938478910176292179410952310592864745025373902249844607078729230098512959498522851990040833671698873183076996740726479481352429756295966452788332789259316653805673821716832204368483794501474641036177256005810416507649770210480747056764697918800240201155395628561684853684747063434500664449114760179367086926249813006056735202795763742271472136500817313178050955623517148960973128433455798444839070215800699075256371341531892841721456473301085595261371522078416420399702683504171019191363372883472415693921509069484448792009627325245658854979159002549542769741504596589556474585723101403486046952706847309188488390899096649210853675228464611999630360164703837131620319658277117300208326944026347808645954842782309633205645471959842390075986572806483755223497552549948718545978420793425036666212191832327909389117021539426917904222971515424022606157676379417252939026404363841301595348953340657745965591468370831371449860774296757556463049237248472613472436666799615694672489600751763956185893123579218797539971253828850163437053164723845196089466298000486042246621634263064752906475198879616484926366053597071510886820878425907736453843197228282179943365206039514850477377542684361730162273246709577442085159313947668552462343596819299335060863266863059421286080919061657175757802930378698062290163092494909661982639303946271889619023417245433500782685534406291391527022657608608130680134939380126048353657648559735671562230714451258764762350451448379438849319710473631625533527602085050858633346936315115309333355986556546113134787213610042970405680162084678021281774169131725296977361816657904233850711837826724976507876061043779177845550646612327663283839673950405472039432309339110648301347672597370034346896334064135099613033528785924976781865447506814375627647103020761819104412269362847848884053177378762432543285984193091289854949394023586451139393716370633759317698908834326333339634557238526607966375935960004339535161203546369910853171524516945554862019134684985868547068709986010719120259421723270478586992153989283736650948010894951434857207445141886625290777550599700738909777829412358941157674866550887608199469723859806486384262574182811908513849905040209776132986875560077482527819093584150609347560543627976011009349905362597935257895287412087233810106693141683912683308201407373637490835862452911394718399632093441745957478079754723679119343225931665785380948807114301164623717144211285944154289093317610519159281033583963015810556464180819928345256832572962092994993950655913067768151113345566231088759030148164710287289335782462899525700500822021472132532771242198844498579102733028256523810973405350508253183399668290339844052874956694050028526577775764032598023622192221226501334606994447870277619118208162133562541678250491647671042612088902952091163094215645902682086024337098910110924115381788866213335441814530141911754446270296630426675020592640816713810936850961517475097707179713115856513919631998747192606018612535436009162735908155778165736923393260822217415131632296810207091918499370220533980666393617256227781299273913099896641458499949922475383775878771011361417556799406151773618626138749998464514570482965286184387350245762317271666329142667987131139265167425606863654107927682419958167046956962340419295394058625063862272314570914511355913547470055072878835349142049813368019960713974852351833144227544851625677753419141348585495260230041111323576432417502998832485027071744397105338790364666312325483218209150368759120749671419554589928540715813531144241705501211397506662448276056294585639532800634727428900861538486753011006379264618338782036690340859441153926551954112364946638768223012718907190897165613382555036872673785444132692292217184974818914501886689736449912131900762592363447945036085692999163815947845753538999001633767986447907729462453017601-
2678543790793380710194816683886586764715440574327327883594135783038388326951102618031717804920971353627844258232176243790989868374810182935778107635972439523097209826418712704526949494602274456264734228022995100733762900266333878923824295581063251019540499205312286060107673239910796787608334357208346488141115751233206821247117649774911446358421536885854186191330548217364994328407469937602370830445520755734810522907314168857091755945971338120859874025301689214000181787843755827144190647800299489027108544741736084811994843732175105699580676435146583437818521058972523643129594128255038848039616185241791693472565589606782879391793446202939373479600778001940012209404435085253728577757396056018945016322316550771772690768597467288463855885527549277571522895996046407650613471074489501660943441073261863732362001630463259688070370208302656561453030347708531676210373694841710965809011985048073324849822507238755151748087849912948712820516770978480576771255815915295719023010110796882699948550648198080664366672315375212762450347734738424306753917308167660660053883558464945875835729821209945420478864136291904610948454592829885024984702246563607038369229862712956016522828830040455871694885183041116740426379476330429723465966082188330127259275053805306921711704204338163794021874638223177207625810184507645206210422637056229297914240240152315395055361678829684701543433803864442878760116867086386849806722056683112795315542267311136437097312662450948229517115210972499833449727444775970215555099067852371292651892193321451326301030955261027722071028420331912682849171012712363305703471791593915421069430928791224227318433658786179158329849533705741448196588894274578621101318186046280806839873188423880898261649203521675148864611149330351240703786391619518658268378300113446943332447799939954781122308609805637819959757470075225272797323755143967551496148711358978325853424299866202495832241969388211021531183917797762970810724013338157607489416346739019521363729241594720653330327745892881467495831364261860678576756836063038375248393693471542266790872694571029599781663946203893048929217801139963261828761203436278264712947195998546297006286033617621518323064058906466458879535124925258053588733510794180877580107723767843106438281141743354574039403290476599942674725730080123245606377434173159210887667564362331662819195945060034666853726421169080918312457165977802810888696772890154144494804981981567603933467889534413415979833490201685416126290360627011919608528700678922539371571048243557647455035660854230619211257692562341507448240858848417010462563625432737600801850845158346833195114446133344964556470323133770213600878970299280161074078009545774088631723983377353910657800493849883737814714976404906060109779168713550528572326738183829233950305452038361709331413648198667671778170022006896247524133939013024769785801016780760847497368375541137101806161810664412155442846687484041209378666412542204184182018289752709393056286439659393625560632399117688011834225233338871557227544607864225934929004329358161102186369023653161110516864174860989934675922868431568709104010706678259295293269525586983127989193496650132610886201434767287444083686616457777447839699914809766185412286441156842466543683608097489722868406480342262494562810796713841451040111276132055775551309482454559092633150602039560455807975282009341189362532445256753087402737233752666692598583905673308146207372930290827903452833054717834832086037745891968078996923672480343144571665192280940907114232044623162144206416944064109092735410513699280960043962291010550920180741028344671832564668092929143949985313062707151037125565238988754134148112750286760935777040899485300500189721466826532709952198120898575025732954396523390273399802508198223398848890334429052834636693755928519031775720462597483622187514226432494606612947864689619081398161665562536987250420367670571412083142952034913093871245900222085980937098692910920847381773206212972241811833141876494446027596627684675003272640465913808591850914657474732307177413115840173919071998746197606000452535287309159781908130148165346323392046822191995131456596808043091901559369859133975797393612416227801599271559099873371458373749921359383740898770744961416740799398401773279626137101998456974570424565284550387336345762296271667001142633967130936365166135606855984107689082419655167030616962291019294220058612663862141314570852511325473547312055073588835354572049786168020885713978772351847244226716851628047753354341349977495251030040893623574990417495888832341227070047397114678790467466311575483228829150361359121719671423114590001540715181531154241705445811396128662449096056345685639196800615247428909261539806753016026379275318340016036700990859483953925783954104904946747368223558718921840897193213383185036875213785261732694338217196754818960901886503736454992131942062592257447937846085796199164450947842813538998101634085986467097729434453017585=
9999601699994313999943589999789299997708999974319999641999998089999958939999675199996811999956919999719399996813999977089999651199996415999949539999534499997113999967909999623599998245999980579999658399997295999964669999755999998804999974659999778999996331999952439999666999995769999982499999830599997981999977939999719199997465999972679999708499998447999971249999790999999520999968419999711499996541999968179999835799998299999982699999638699997903999967379999643199996664999984499999799599997593999981699999793799996277999956959999653499997919999977569999870599998236999976859999772099998551999980979999937999999435999987859999774899997791999986159999779999997534999982739999865399998075999981459999807999998646999978039999785799999197999994709999863999997478999982699999727599999591999971200000292200001699000022160000210000001398000017570000222600001000000031900000194400002546000017080000127600001807000026340000095600002202000023310000253600001483000028700000302200003064000015000000358600002660000031200000268700003164000012850000280800002028000032320000424300005122000026870000410200003518000046040000274800003856000034860000389200003281000040360000235800003482000023160000377800003988000035880000300100005022000032830000370600002662000041600000366900005128000030320000479600002813000048380000232000004564000058110000535400004560000048840000573200006024000045520000696800006236000062500000539400006284000052090000448200004161000063720000515600007394000033750000628600006071000063100000245600007404000048880000648400005147000054640000343800007388000067790000655000006479000067180000624100006088000053520000785400006812000068800000672700009064000056400000662200007102000085300000671900007436000064510000835000007332000079600000850300008924000050740000801000008739000094880000693900008706000061660001023400007652000084920000761300009160000079530001053800007187000094940000736800009696000085940000906000008243000106460000704700009268000068890000906200006883000112060000628300010330000072710000875000007188000095720000720400010862000078920000894400008743000101460000970100009982000074650000996400007992000088960000774900010898000090920000994200008629000115940000694000008740000081360001108000008338000092640000845800012686000090790001038200010632000111560000777600009636000082150001103200007912000103060000988100011934000103390000828600009333000117000000749200009780000119490001289400008948000104680001071700012804000084610001265600010581000118280001030900010738000079430001212400008555000110100001104700010708000095240001072200008944000138580000902700011068000100790001283200013475000103120000863200011022000075790001017000009164000106400001010600011736000080500001313600007906000103740000828100012010000102970000934000009132000118040000925100010440000100020001070600007697000102680000819200012340000086540001160600008759000123960001104600009446000086510001214600008440000113920001161400011968000096020001081800011073000102240000967300011480000090810001360200010897000101100000763000010982000102150001031000010177000101360000887200010414000081380001029200009063000115500000882000012442000126430000953000009026000090240000815400008750000089920001058200008833000102760000824100011644000072500000832400007204000101980000991400006042000079620001111800008454000098500000931100008768000073260000951000007308000087820000729000008716000065490001142200009350000057440000543100007010000055200000707200007959000078340000564800007404000065510000757800006639000081360000593100007900000069120000555000004869000090180000582200005460000073540000724800005544000078900000585000008294000065850000670600005061000076220000992100004896000051960000528400005422000040400000632300005306000061290000723600004077000073860000420700005548000054960000819400005415000040320000294100007546000043570000540000004707000068840000381500005588000036810000468000004691000071280000471200005760000056250000344400002460000043400000217200003268000015660000363200002697000035260000242700002742000017320000350800002345000046860000365400002300000016340000560000000995000018160000148700002954000025630000390600001214000025420000175700002164000016940000361400004869000004839999979700002354000023270000126200001116000034980000266400000816000007750000339000001648000007540000058400001634000013900000020999999328000034020000202900001290000007670000238600000303000016340000049400001174000012400000131000000062000030440000157999999289999994570000027199999074999996079999985900000827999997630000064799998608000009200000217700001442000007110000143800001696999990659999897200000749999989380000007399999029999996439999927000000631999990000000055400001377999999179999948900000336000019479999991599998679999994979999989299998765999989349999957200000768000007459999891399999453999985349999972399999369999997460000182399997953999988219999953600000185999994919999958700000106000007189999896799999365000002940000000899999681999980810000028000000016.

看起来二者差得很多，这个算法不对了，少了很多。

398300005686000056410000210700002291000025680000358000001910000041060000324800003188000043080000280600003186000022910000348800003584000050460000465500002886000032090000376400001754000019420000341600002704000035330000244000001195000025340000221000003668000047560000333000004230000017500000169400002018000022060000280800002534000027320000291500001552000028750000209000000479000031580000288500003458000031820000164200001700000017300000361300002096000032620000356800003335000015500000200400002406000018300000206200003722000043040000346500002080000022430000129400001763000023140000227900001448000019020000062000000564000012140000225100002208000013840000220000002465000017260000134600001924000018540000192000001353000021960000214200000802000005290000136000002521000017300000272400000408000028799999707799998300999977839999789999998601999982429999777399998999999968099999805599997453999982919999872399998192999973659999904399997797999976689999746399998516999971299999697799996935999984999999641399997339999968799999731299996835999987149999719199997971999967679999575699994877999973129999589799996481999953959999725199996143999965139999610799996718999959639999764199996517999976839999622199996011999964119999699899994977999967169999629399997337999958399999633099994871999969679999520399997186999951619999767999995435999941889999464599995439999951159999426799993975999954479999303199993763999937499999460599993715999947909999551799995838999936279999484399992605999966249999371399993928999936899999754399992595999951119999351599994852999945359999656199992611999932209999344999993520999932819999375899993911999946479999214599993187999931199999327299990935999943599999337799992897999914699999328099992563999935489999164999992667999920399999149699991075999949259999198999991260999905119999306099991293999938339998976599992347999915079999238699990839999920469998946199992812999905059999263199990303999914059999093999991756999893539999295299990731999931109999093799993116999887939999371699989669999927289999124999992811999904279999279599989137999921079999105599991256999898539999029899990017999925349999003599992007999911039999225099989101999909079999005799991370999884059999305999991259999918639998891999991661999907359999154199987313999909209998961799989367999888439999222399990363999917849998896799992087999896939999011899988065999896609999171399990666999882999999250799990219999880509998710599991051999895319998928299987195999915389998734399989418999881719998969099989261999920569998787599991444999889899998895299989291999904759998927799991055999861419999097299988931999899209998716799986524999896879999136799988977999924209998982999990835999893599998989399988263999919499998686399992093999896259999171899987989999897029999065999990867999881959999074899989559999899979998929399992302999897319999180799987659999913459998839399991240999876039998895399990553999913489998785399991559999886079998838599988031999903979998918199988926999897759999032699988519999909189998639799989102999898899999236999989017999897849998968999989822999898639999112799989585999918619998970799990936999884499999117999987557999873569999046999990973999909759999184599991249999910079998941799991166999897239999175899988355999927499999167599992795999898019999008599993957999920379998888199991545999901499999068899991231999926739999048999992691999912179999270999991283999934509998857799990649999942559999456899992989999944799999292799992040999921659999435199992595999934489999242199993360999918639999406899992099999930879999444999995130999909819999417799994539999926459999275199994455999921099999414999991705999934149999329399994938999923779999007899995103999948039999471599994577999959599999367699994693999938709999276399995922999926139999579299994451999945039999180599994584999959679999705899992453999956429999459999995292999931159999618499994411999963189999531999995308999928719999528799994239999943749999655599997539999956599999782799996731999984339999636799997302999964739999757299997257999982679999649199997654999953139999634599997699999983659999439999999004999981839999851299997045999974369999609399998785999974579999824299997835999983059999638599995130999995160000020299997645999976729999873799998883999965019999733599999183999992249999660999998351999992459999941599998365999986099999979000000671999965979999797099998709999992329999761399999696999983659999950599998825999987599999868999999937999969559999842000000710000005429999972800000925000003920000014099999172000002369999935200001391999990799999782299998557999992889999856199998303000009340000102799999250000010619999992600000970000003560000072999999368000009999999944599998622000000820000051099999663999980520000008400001320000005020000010700001234000010650000042799999231999992540000108600000546000014650000027600000630000002539999817600002046000011780000046399999814000005080000041299999893999992810000103200000634999997059999999100000318000019189999971999999984.
这个有4884位，是减数和被减数反过来减的，看起来被减数（正确值）是小的，错误结果反而是大的。上面的差值是4888位，最高位是9就是比被减数还大，是错误的，我的减法是可以这样算的，最高位算起的，最高位前面没有数字了，其实前面应该剩下个-1，哈哈哈！该程序的缺点，不判断两个数的大小，应该先判断，再有大的减小的，被减数小的话输出负值，并反过来算就对了，仅从乘法结果的末尾看，错误的数字是3017585，正确的数字是3017601，似乎仅仅差末尾3位，其实前面有很多数字是不对的，而错误结果其实是大于实际值的。

[此贴子已经被作者于2021-3-20 02:41编辑过]

11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111（329位，329个1）*101=11111111111111111111111111111111111111111111111122222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222211有377位，用时0.2773438秒（331位是正确的，多了46个1）。

[此贴子已经被作者于2021-3-20 08:10编辑过]

51750801837147361345408953922231823615475578427966187002956389087112242842559611794590895524485015222232340190036677951157401229518412775512617768569186939216558814320044037671525512763073762127357272238470370174050144130962253437215369727381909754581075278888137687950749577751967083233227932391898438489520107788418593104216764745143648165875043861634459264809523254076330115365651752264033578829280651927862062277153553168278640509846511729608378923480331705134467105387853440058108864733429085916392927954109944314725590758950098556991513109760871599045355054258610189920009222629391227784118536578933067532162200768112408111142115021110731900107445187734955403922470144187293970602024056652942406064101184615113779243566842311336047149767396006622923831778833173731302325162741660053390002572456069410383734906953419854919650114722834689335022576764661864630532595250136417800041415827379233503655173380741283758557001102498493237113089198106283487003030225058520047964863929279622015825870972146222540614667928697270131499340362072956956518213266361286372027834000838185920579641835952404678850816456467012890793914108776148483471455515695596694573035435841962871983614397882366460940068418989292218104650923374259244879331938925143014431488635252724366437874702141802712286424754174951797598162531093933772708024046029028652425912112434874797404878317364682580259997737809632860143160557722236459697738869857870982308547756781808568834445404196611833859447257611721058384661943492980180884154939581533269700568975940675513953240040220315659784214936947443784598154082110443748171557676558299300252057475022409541083454882202785077569281268346332901357829843950754331120530978456454396022570647840977328115888711408099894489014427119253061839770890965114853246067272044090282103668762164047374624856119676063310166566519499552342907590495696658359542582469176737197423550084705962160477441546453931948920780829433665262356431973422034925001341330921812806939990688094288773216182971976433480031438271163051341645350474631300965486818841553843112688792803367397276204832936049162335586140151875524537720425345701193713093955432559579831822084761702059241698184717469616732582600658006352069963017377661059372648121969448644394344799369193952197519795756182552461838014896498816263546256621347748100920475049252091842372001283217811864786225692344297842649982716736752004086642881662614773154743879410328420184057019873899911520017723788801*
51750801837147361345408953922231823615475578427966187002956389087112242842559611794590895524485015222232340190036677951157401229518412775512617768569186939216558814320044037671525512763073762127357272238470370174050144130962253437215369727381909754581075278888137687950749577751967083233227932391898438489520107788418593104216764745143648165875043861634459264809523254076330115365651752264033578829280651927862062277153553168278640509846511729608378923480331705134467105387853440058108864733429085916392927954109944314725590758950098556991513109760871599045355054258610189920009222629391227784118536578933067532162200768112408111142115021110731900107445187734955403922470144187293970602024056652942406064101184615113779243566842311336047149767396006622923831778833173731302325162741660053390002572456069410383734906953419854919650114722834689335022576764661864630532595250136417800041415827379233503655173380741283758557001102498493237113089198106283487003030225058520047964863929279622015825870972146222540614667928697270131499340362072956956518213266361286372027834000838185920579641835952404678850816456467012890793914108776148483471455515695596694573035435841962871983614397882366460940068418989292218104650923374259244879331938925143014431488635252724366437874702141802712286424754174951797598162531093933772708024046029028652425912112434874797404878317364682580259997737809632860143160557722236459697738869857870982308547756781808568834445404196611833859447257611721058384661943492980180884154939581533269700568975940675513953240040220315659784214936947443784598154082110443748171557676558299300252057475022409541083454882202785077569281268346332901357829843950754331120530978456454396022570647840977328115888711408099894489014427119253061839770890965114853246067272044090282103668762164047374624856119676063310166566519499552342907590495696658359542582469176737197423550084705962160477441546453931948920780829433665262356431973422034925001341330921812806939990688094288773216182971976433480031438271163051341645350474631300965486818841553843112688792803367397276204832936049162335586140151875524537720425345701193713093955432559579831822084761702059241698184717469616732582600658006352069963017377661059372648121969448644394344799369193952197519795756182552461838014896498816263546256621347748100920475049252091842372001283217811864786225692344297842649982716736752004086642881662614773154743879410328420184057019873899911520017723788801=
2678145490787694710138406683675886762424440548647327525594133873038347266950777818028529804877891353347244255046176220880989519574806598935727647635506939520211209794328712328126947740602255036264392628020291100698432900022333877728824270241063030019536831205264726059774673235680796770108334187808344470141093691232926021244583649747591446066921535333854157441330339217364515328375889937313870826987520723914810358707312468857074455945610038118763873992681688857200178452843740327143990247797893489008808544535536081089994800692174759199578596435124153437689121057209523619989593900355037400039597165241729693472001589594642879166693443994939359639600558001937547209387175085119128575833396037478944824322315197771750730768383267287661855880237549141571520374996029107650341071074081501632143441365461865431362023790463469688071768208320226561675630348708531708110373889241713511809029065048200924851629507265095151843687852114948736130517024578482059771284515915597919026074110811882700307150650858080695566672584075215926450360584738705106755945308199980660478183563586945902705730231409948938478910176292179410952310592864745025373902249844607078729230098512959498522851990040833671698873183076996740726479481352429756295966452788332789259316653805673821716832204368483794501474641036177256005810416507649770210480747056764697918800240201155395628561684853684747063434500664449114760179367086926249813006056735202795763742271472136500817313178050955623517148960973128433455798444839070215800699075256371341531892841721456473301085595261371522078416420399702683504171019191363372883472415693921509069484448792009627325245658854979159002549542769741504596589556474585723101403486046952706847309188488390899096649210853675228464611999630360164703837131620319658277117300208326944026347808645954842782309633205645471959842390075986572806483755223497552549948718545978420793425036666212191832327909389117021539426917904222971515424022606157676379417252939026404363841301595348953340657745965591468370831371449860774296757556463049237248472613472436666799615694672489600751763956185893123579218797539971253828850163437053164723845196089466298000486042246621634263064752906475198879616484926366053597071510886820878425907736453843197228282179943365206039514850477377542684361730162273246709577442085159313947668552462343596819299335060863266863059421286080919061657175757802930378698062290163092494909661982639303946271889619023417245433500782685534406291391527022657608608130680134939380126048353657648559735671562230714451258764762350451448379438849319710473631625533527602085050858633346936315115309333355986556546113134787213610042970405680162084678021281774169131725296977361816657904233850711837826724976507876061043779177845550646612327663283839673950405472039432309339110648301347672597370034346896334064135099613033528785924976781865447506814375627647103020761819104412269362847848884053177378762432543285984193091289854949394023586451139393716370633759317698908834326333339634557238526607966375935960004339535161203546369910853171524516945554862019134684985868547068709986010719120259421723270478586992153989283736650948010894951434857207445141886625290777550599700738909777829412358941157674866550887608199469723859806486384262574182811908513849905040209776132986875560077482527819093584150609347560543627976011009349905362597935257895287412087233810106693141683912683308201407373637490835862452911394718399632093441745957478079754723679119343225931665785380948807114301164623717144211285944154289093317610519159281033583963015810556464180819928345256832572962092994993950655913067768151113345566231088759030148164710287289335782462899525700500822021472132532771242198844498579102733028256523810973405350508253183399668290339844052874956694050028526577775764032598023622192221226501334606994447870277619118208162133562541678250491647671042612088902952091163094215645902682086024337098910110924115381788866213335441814530141911754446270296630426675020592640816713810936850961517475097707179713115856513919631998747192606018612535436009162735908155778165736923393260822217415131632296810207091918499370220533980666393617256227781299273913099896641458499949922475383775878771011361417556799406151773618626138749998464514570482965286184387350245762317271666329142667987131139265167425606863654107927682419958167046956962340419295394058625063862272314570914511355913547470055072878835349142049813368019960713974852351833144227544851625677753419141348585495260230041111323576432417502998832485027071744397105338790364666312325483218209150368759120749671419554589928540715813531144241705501211397506662448276056294585639532800634727428900861538486753011006379264618338782036690340859441153926551954112364946638768223012718907190897165613382555036872673785444132692292217184974818914501886689736449912131900762592363447945036085692999163815947845753538999001633767986447907729462453017601有4888位，用时9.912109秒（这个看上去是对的，用时和手工计算差不多，还略多一点？）

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！）