C++ RSS C++ RSS

help with factorial recursive

Please support our C++ advertiser: Intel Parallel Studio Home
Reply

•
•
Join Date: Dec 2008
Posts: 1,280
Reputation: firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice 
Solved Threads: 157
firstPerson's Avatar
firstPerson firstPerson is online now Online
Nearly a Posting Virtuoso

help with factorial recursive

 
0
  #1
Dec 30th, 2008
C++ Syntax (Toggle Plain Text) 
  1. #include<iostream>
  2. #include<fstream>
  3. #include<cmath>
  4. #include<iomanip>
  5.  
  6. using namespace std;
  7. unsigned __int64 Fact(unsigned __int64 x );
  8.  
  9.  
  10. int main(){
  11.  
  12. 	/*n! means n  (n  1)  ...  3  2  1
  13.  
  14. Find the sum of the digits in the number 100!*/
  15.  
  16.  
  17. cout<<Fact(100);
  18.  
  19.  
  20. }
  21. unsigned __int64 Fact(unsigned __int64 x )
  22. {
  23. 	__int64 num(0);
  24.  
  25. 	if(x==0)
  26. 		return 1;
  27. 	else
  28. 	{
  29. 	 num = x * Fact(x-1);
  30. 	 cout<<num<<"  "<<x<<endl;
  31. 	}
  32.  
  33. 	return num;
  34. }


my recursive function works. But only for small x. (ex. 5! =120).

but when i try (100!) it runs out of space and give NULL;

so can you hint on how i can fix the code so that the computer will compute 100factorial?
Reply With Quote Quick reply to this message  
•
•
Join Date: Dec 2008
Posts: 1,280
Reputation: firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice 
Solved Threads: 157
firstPerson's Avatar
firstPerson firstPerson is online now Online
Nearly a Posting Virtuoso

Re: help with factorial recursive

 
0
  #2
Dec 30th, 2008
OK here is a little improved version of it. Now it finds at maximum of
65!. Any hints on how to find 100!
C++ Syntax (Toggle Plain Text) 
  1. #include<iostream>
  2. #include<fstream>
  3. #include<cmath>
  4. #include<iomanip>
  5.  
  6. using namespace std;
  7. unsigned __int64 Fact(unsigned __int64 x );
  8.  
  9.  
  10. int main(){
  11.  
  12. 	/*n! means n  (n  1)  ...  3  2  1
  13.  
  14. Find the sum of the digits in the number 100!*/
  15.  
  16. //unsigned __int64 * fact = new unsigned __int64 (10000);
  17.  
  18. Fact(100);
  19.  
  20. }
  21. unsigned __int64 Fact(unsigned __int64 x )
  22. {
  23. 	unsigned __int64 * fact = new unsigned __int64 (10000);
  24. 	*fact = x;
  25.  
  26. 	if(x==0)
  27. 		return 1;
  28. 	else
  29. 	{
  30. 	 *fact = x * Fact(x-1);
  31. 	 cout<<*fact<<"  "<<x<<endl;
  32. 	}
  33.  
  34. 	return *fact;
  35. 	delete fact;
  36. }
Reply With Quote Quick reply to this message  
•
•
Join Date: Nov 2008
Posts: 963
Reputation: MosaicFuneral is just really nice MosaicFuneral is just really nice MosaicFuneral is just really nice MosaicFuneral is just really nice MosaicFuneral is just really nice 
Solved Threads: 92
MosaicFuneral's Avatar
MosaicFuneral MosaicFuneral is offline Offline
Posting Shark

Re: help with factorial recursive

 
0
  #3
Dec 30th, 2008
Can't you use a loop instead?

You could create a class that grows and manages the value split over vectors, overloads the general math operators you'd need, then stores the values into a file.
"Jedenfalls bin ich überzeugt, daß der Alte nicht würfelt."
"I became very sensitive to what will happen to all this and all of us." -Two geniuses named Albert
Reply With Quote Quick reply to this message  
•
•
Join Date: Dec 2008
Posts: 1,280
Reputation: firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice firstPerson is just really nice 
Solved Threads: 157
firstPerson's Avatar
firstPerson firstPerson is online now Online
Nearly a Posting Virtuoso

Re: help with factorial recursive

 
0
  #4
Dec 30th, 2008
checked again anything over 20! is not correct. anyhelp?
Reply With Quote Quick reply to this message  
•
•
Join Date: Apr 2006
Posts: 357
Reputation: death_oclock will become famous soon enough death_oclock will become famous soon enough 
Solved Threads: 37
death_oclock's Avatar
death_oclock death_oclock is offline Offline
Posting Whiz

Re: help with factorial recursive

 
0
  #5
Dec 31st, 2008
Check out GMP (Gnu MultiPrecision). It allows you to work with extremely large numbers and has wrappers for c++.
Reply With Quote Quick reply to this message  
•
•
Join Date: Aug 2008
Posts: 206
Reputation: grumpier has a spectacular aura about grumpier has a spectacular aura about 
Solved Threads: 31
grumpier grumpier is offline Offline
Posting Whiz in Training

Re: help with factorial recursive

 
1
  #6
Dec 31st, 2008
To give you a clue about what's happening, 100! is about 9.3 by 10^157. To represent that, a 525 bit integer is needed (and that increases 530 bits to represent 101!). 64 bit is nowhere near enough: an unsigned 64 bit integer can only represent a maximum value of about 18446744073709551615 (approx 1.8 by 10^19).
Reply With Quote Quick reply to this message  
Reply

Quick Reply to Thread
This thread is more than three months old.
Perhaps start a new thread instead?
•
•
•
•
•
•
•
•
Message:
•
•
•
•



Similar Threads
Other Threads in the C++ Forum
Thread Tools Search this Thread



api array arrays based beginner binary bitmap c++ c/c++ calculator char char* class classes code coding compile compiler console conversion convert count data database delete deploy developer dll download dynamiccharacterarray email encryption error file forms fstream function functions game generator getline givemetehcodez graph gui homeworkhelp homeworkhelper iamthwee ifstream input int java lib list loop looping loops map math matrix memory multiple news node number numbertoword output parameter pointer problem program programming project proxy python random read recursion recursive reference rpg sorting string strings temperature template text text-file tree url variable vector video visual visualstudio win32 windows winsock word wordfrequency wxwidgets
About Us | Contact Us | Advertise | DaniWeb | Acceptable Use Policy | RSS Feed

©2003 - 2009 DaniWeb® LLC