一道面试题, 求 1000！的位数(VBS实现)
一道面试题, 求 1000！的位数(VBS实现) http://community.csdn.net//Expert/TopicView2.asp?id=4498174&datebasetype=now Option Explicit
'VBS 实现求 1000! 位数
'作者: xiaoyuehen(萧月痕)
'日期: 2006-1-6
'MSN: xiaoyuehen(at)msn.com
'大数加法
'参数 x: 加数, y: 被加数
'以数组存储
Dim arrR(), strX, strY, lx, ly
strX = StrReverse(x)
strY = StrReverse(y)
lx = Len(strX)
ly = Len(strY)
'Msgbox lx
Dim i, iMax, iJinWei
If lx > ly Then
iMax = lx
Else
iMax = ly
End If
ReDim arrR(iMax)
iJinWei = 0
For i = 1 to iMax
arrR(i) = int('0' & Mid(strX, i, 1)) + int('0' & Mid(strY, i, 1)) + iJinWei
iJinWei = arrR(i) \ 10
arrR(i) = Right(arrR(i), 1)
Next
Dim strResult
strResult = StrReverse(Join(arrR, ''))
If Left(strResult, 1) = '0' Or iJinWei = 1 Then
strResult = '1' & strResult
End If
GetAddResult = strResult
End
'以字符串构造
'该方法经过试验不可行..速度太慢!
Dim strX, strY, lx, ly
strX = StrReverse(x)
strY = StrReverse(y)
lx = Len(strX)
ly = Len(strY)
Dim i, iMax, iJinWei
If lx > ly Then
iMax = lx
Else
iMax = ly
End If
Dim iTemp, strResult
iJinWei = 0
iTemp = 0
For i = 1 to iMax
iTemp = int('0' & Mid(strX, i, 1)) + int('0' & Mid(strY, i, 1)) + iJinWei
iJinWei = iTemp \ 10
strResult = (iTemp Mod 10) & strResult
Next
If Left(strResult, 1) = '0' Or iJinWei = 1 Then
strResult = '1' & strResult
End If
GetAddNResult = strResult
End
GetMulResult = 0
Dim i
For i = 1 to y
GetMulResult = GetAddResult(GetMulResult, x)
Next
End
GetMultResult = 0
Dim str, lx, ly, i
ly = Len(y)
For i = 1 to ly
GetMultResult = GetAddResult(GetMultResult, GetMulResult(x, CInt(Mid(y, i, 1))) & String(ly - i, '0'))
Next
End
If Len(x) > Len(y) Then
GetMulcResult = GetMultResult(x, y)
Else
GetMulcResult = GetMultResult(y, x)
End If
End
GetFactorialResult = x
Dim i
For i = (x - 1) to 2 step - 1
GetFactorialResult = GetMulcResult(GetFactorialResult, i)
Next
End
'原作: aiur2000(闭关失败，走火入魔，开关拉！)
'vbs代码实现: xiaoyuehen
Dim iLen, iSum, iVal, i
'思路:因为不计算具体值,所以没必要全部算出,只用计算能影响到结果的位数即可,同时要加入下次影响结果的值.
'做法:每次的积取下次乘数的位数的2倍即可.
'下一个乘数的位数
iLen = 0
'位数
iSum = 0
'积
iVal = 1
For i = 1 to x
iLen = Len(i)
'如果积超过乘数位数2倍,后面的记入汇总位数
If Len(iVal) > iLen * 2 Then
iSum = iSum + (Len(iVal) - iLen * 2)
iVal = Left(iVal, iLen * 2)
End If
iVal = iVal * i
Next
GetFactorialLength = Len(iVal) + iSum
End
t = Timer
x = String(1000, '9')
y = String(1000, '9')
'y = String(200, '9')
'Msgbox ' String 总用时: ' & FormatNumber(Timer - t) & ' 秒'
't = Timer
'Call GetAddResult(x, y)
'Msgbox ' GetAddResult: ' & 'GetAddResult(x, y)' & ' 总用时: ' & FormatNumber(Timer - t) & ' 秒'
t = Timer
'Call GetFactorialLength(1000)
Msgbox ' GetFactorialLength(1000): ' & GetFactorialLength(1000) & ' 总用时: ' & FormatNumber(Timer - t) & ' 秒'
't = Timer
'Call GetMulResult(x, y)
'Msgbox ' GetMulResult: ' & GetMulResult(x, y) & ' 总用时: ' & FormatNumber(Timer - t) & ' 秒'
't = Timer
'Call GetMulResult(x, y)
'Msgbox ' GetMultResult: ' & GetMultResult(x, y) & ' 总用时: ' & FormatNumber(Timer - t) & ' 秒'
't = Timer
'Call GetMulResult(x, y)
'Msgbox ' GetMulcResult: ' & GetMulcResult(x, y) & ' 总用时: ' & FormatNumber(Timer - t) & ' 秒'
't = Timer
'Call GetAddResult(x, y)
'Msgbox ' GetAddResult 总用时: ' & FormatNumber(Timer - t) & ' 秒'
't = Timer
'Call GetAddNResult(x, y)
'Msgbox ' GetAddNResult 总用时: ' & FormatNumber(Timer - t) & ' 秒'
'x = 300
't = Timer
'Call GetFactorialResult(x)
'Msgbox ' GetFactorialResult(' & x & ') = ' & GetFactorialResult(x) & ' 总用时: ' & FormatNumber(Timer - t) & ' 秒'
'Msgbox ' 共 ' & Len(GetFactorialResult(x)) & ' 位, 用时: ' & FormatNumber(Timer - t) & ' 秒'