WA in Virat and nCr

#1

I have used fermat’s little theorem to solve this problem but still getting wrong answer on some testcase. Please suggest some way to rectify it.
Code: https://ide.codingblocks.com/s/94157

#2

it is about calculating factorials under modula,
than taking inverses

#3

nCr= N!*inverse(R!)*inverse(N-R!)

#4

That;s what I’m doing I guess.
I first calculated factorials of r! and (n-r)! using
ll temp1=fac[r];
ll temp2=fac[n-r];
and then put power (p-2) over it.
What changes should I make?

#5

multiply in steps;
meaning
ans=(abc)%mod;
so you do it like
ans=(ab)%mod;
and then–
ans=(ansc)%mod;
to avoid interger overflows

1 Like
#6

i have made the modifications -
check it

1 Like
#7

Thanks
Got accepted :slight_smile:
Can you mark this issue resolved from your side as I’m not able to mark it down because of some technical fault.

#8

yeah sure…