I am searching for a good tutorial for fast polynomial multiplication (better than O(n^2)). I know that Fast fourier transformation can be used but i am not able to understand it at all. someone plz share the link of good tutorial for fast polynomial multipication problem.

The best source for this is Cormen itself… For implementation part see this

https://www.codechef.com/viewsolution/8318645

I applied the concept in OCT 15 KSPHERES…Although i messed up with the modulo thing but i believe the idea is correct…

your solution is in C++…!! it is difficult for me to interpret it bcoz i know only C language. Do you any solution in C language…??