Faster implementation using math.Abs and switch

#### Is your solution the most efficient way to solve a problem? Why? - It's twice as fast as current solution #### Have you used any specific algorithm? - No, it uses math.Abs instead of hand written abs function. - I think using 'switch' for co-ord check is a little more readable than the 'if' check - I use co-ords based on 1 instead of 0 for readability. #### What is time and space complexity of your solution? - time is a half of current solution (120 ns/op vs 240 ns/op) on my machine - I don't think there are any space issues, 58 lines of code vs 38.