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        riddles >> cs >> 100!
        
(Message started by: sat90 on Aug 14^th, 2011, 12:05pm)

Title: 100!
Post by sat90 on Aug 14^th, 2011, 12:05pm

whats the logic behind calculating 100!......w/o using any bigint lib

Title: Re: 100!
Post by SMQ on Aug 15^th, 2011, 9:19am

Since 100! has 158 (decimal) digits, you're going to be hard-pressed to calculate the exact result without an arbitrary-precision math library of some sort. However you can, for instance, count the number of zeros at the end w/o a bigint library.

--SMQ

Title: Re: 100!
Post by towr on Aug 15^th, 2011, 1:14pm

It's not that hard to implement the method of multiplication you learned in school. Although it's not very efficient, it'll get the job done.

Title: Re: 100!
Post by Grimbal on Aug 22^nd, 2011, 5:07am

Or you can apply the method you learned at school. With a pencil, paper and lots of time.
100! should still be feasible.

Title: Re: 100!
Post by towr on Aug 22^nd, 2011, 8:43am

It's easy to make mistakes by hand, though.

Title: Re: 100!
Post by sat90 on Sep 5^th, 2011, 6:10am

i m not able to simulate manual multiplication using algorithm...plz help!!

Title: Re: 100!
Post by towr on Sep 5^th, 2011, 8:49am

Something like:

Pseudo
Code:

int A[200] = {0};
A[0]=1;
for(C=2; i <=100; i++)
{
temp = 0;
for(i=0; i < 200; i++)
{
temp += C * a[i];
A[i] = temp % 10;
temp /= 10;
}
}

for(i=200; i > 0 && A[i] == 0; i--)
;

for(; i >=0; i--)
cout << a[i];