LeetCode Q149: Max Points on a Line (hard)

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

Solution:

Using hash, for each point, check the number of all other points that are co-linear with current point. The problem will encounter is how to represent a line in hash map. Directly using float/double as slope will have precision problem. So, here I represent a slope using x and y, where x=p1.x-p0.x, y=p1.y-p0.y. Then to ensure uniqueness of each slope, x and y are divided by their GCD.