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Big numbers
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Hey... do anyone knows c++ function for implementation of big numbers...i tried googl it...but, i can't find nothing that solve my problem
i need to calculate a^e(mod n)
example:
125^107 (mod 187)=5
result of 125^107 is too big for standard notation in c++...
can someone please help me!
i need to calculate a^e(mod n)
example:
125^107 (mod 187)=5
result of 125^107 is too big for standard notation in c++...
can someone please help me!
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Join Date: Aug 2005
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Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
Now I have problem with fmod...
i calculated with y=pow(a,e)
then fmod(y,n)... but now i seems that that fmod has to small range of results (same thing is with %)
is there some other function for mod?
i calculated with y=pow(a,e)
then fmod(y,n)... but now i seems that that fmod has to small range of results (same thing is with %)
is there some other function for mod?
Last edited by nameless987; Sep 12th, 2008 at 8:25 am.
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Join Date: Dec 2007
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Posting Whiz in Training
Use the GMP library. It works for me. If you're using Dev-C++, you can just search for packages online with the built in "Check for updates/packages" thing, and find it in the list. If not go here: http://gmplib.org/
"Always program as if the person who will be maintaining your program is a violent psychopath that knows where you live."
--Martin Golding
--Martin Golding
How to instal GMP library....dev c++ won'r downlod it, and i don't knoe how to install one i have downloaded from http://gmplib.org/
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Join Date: Aug 2008
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Posting Whiz in Training
Talking about using a sledgehammer to crack a nut. No need to use high precision integers at all.
(a^b) mod c can be evaluated using a loop, using modulo arithmetic.
The basic property you need to know is that (x*y) mod z is equal to ((x mod z)*(y mod z)) mod z). From that it is possible to compute (a^b) mod c. I'll leave the precise code as an exercise.
(a^b) mod c can be evaluated using a loop, using modulo arithmetic.
The basic property you need to know is that (x*y) mod z is equal to ((x mod z)*(y mod z)) mod z). From that it is possible to compute (a^b) mod c. I'll leave the precise code as an exercise.
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Join Date: Dec 2007
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Posting Whiz in Training
Dev-C++ WILL download it. You have to pick the option in the package downloader that says community devpaks, scroll down and find it. Download it, and it should automatically bring you to an installer.
Last edited by TheBeast32; Sep 12th, 2008 at 2:52 pm.
"Always program as if the person who will be maintaining your program is a violent psychopath that knows where you live."
--Martin Golding
--Martin Golding
I tried to download it in that way...but i get some error that this file doesn't exist..
i figured out that i must use this kind calculations if i want to work with big nombers:
P = Cd % n
= 62^65 % 133
= 62 * 62^64 % 133
= 62 * (62^2)32 % 133
= 62 * 3844^32 % 133
= 62 * (3844 % 133)^32 % 133
= 62 * 120^32 % 133
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.
.
= 62 * 36^16 % 133
= 62 * 99^8 % 133
= 62 * 92^4 % 133
= 62 * 85^2 % 133
= 62 * 43 % 133
= 2666 % 133
= 6
How can i write this in c++?
please help
i figured out that i must use this kind calculations if i want to work with big nombers:
P = Cd % n
= 62^65 % 133
= 62 * 62^64 % 133
= 62 * (62^2)32 % 133
= 62 * 3844^32 % 133
= 62 * (3844 % 133)^32 % 133
= 62 * 120^32 % 133
.
.
.
= 62 * 36^16 % 133
= 62 * 99^8 % 133
= 62 * 92^4 % 133
= 62 * 85^2 % 133
= 62 * 43 % 133
= 2666 % 133
= 6
How can i write this in c++?
please help
•
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Join Date: Dec 2007
Posts: 236
Reputation:
Solved Threads: 6
Posting Whiz in Training
i'll attack the devpak! =)
"Always program as if the person who will be maintaining your program is a violent psychopath that knows where you live."
--Martin Golding
--Martin Golding
•
•
Join Date: Aug 2008
Posts: 206
Reputation:
Solved Threads: 31
Posting Whiz in Training
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Originally Posted by nameless987 
i figured out that i must use this kind calculations if i want to work with big nombers:
P = Cd % n
= 62^65 % 133
= 62 * 62^64 % 133
= 62 * (62^2)32 % 133
= 62 * 3844^32 % 133
= 62 * (3844 % 133)^32 % 133
= 62 * 120^32 % 133
.
.
.
= 62 * 36^16 % 133
= 62 * 99^8 % 133
= 62 * 92^4 % 133
= 62 * 85^2 % 133
= 62 * 43 % 133
= 2666 % 133
= 6
How can i write this in c++?
please help
Last edited by grumpier; Sep 13th, 2008 at 1:13 am.
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