I was solving the question http://codeforces.me/contest/227/problem/A. If the cross product is zero then obviously they are collinear since sin(x)=0 if x=2*n*PI. However, how do they decide if it is Left or Right based on the value of cross-product i.e; x1*y2-x2*y1. Please demystify this for me. Am I missing any fundamentals?
C++