help with combinations !!!!

[ayan2587]

hi frndz....

i was wondering that given
1<n<1000000 &
1<r<1000000

how do i efficiently find nCr (combination) for any given values of n & r.

please help with an efficient algorithm...

[clandestine_j]

Please try to write some code first and then we can help you with that. Alternatively, write some pseudocode so we can see what conceptual issues you are having.
~j

[iAmLast]

are those bits???
is n and r integers???

how about stating your problem clearly
and with your code...

>..<

[ayan2587]

I Would elaborate the question:

since n & r values could be very large, and in order to find nCr, n! & r! would have to be calculated, so it is not possible to define a datatype that can hold these factorial values...

instead what i planned to do was that in order to find the factorial, i could create an array, that could hold the values of the multiplication.

for ex: if i have to find 10!,
i wud create an array and store the values as
3 6 2 8 8 0 0 .
so instead of storing the whole value as some datatype, i can
store each value at continuous locations in the array.

but the problem here is, this method will have to be applied both in numerator & denominator, so what i am unable to figure out is how to solve it efficiently.

i hope the problem's much clearer now... :)