149. Max Points on a Line
这道题的想法还是挺简单的，只是要分清三种情况，点的横坐标相同，点重合，其它情况。

# Definition for a point.
# class Point(object):
#     def __init__(self, a=0, b=0):
#         self.x = a
#         self.y = b
import numpy as np
class Solution(object):
    def maxPoints(self, points):
        """
        :type points: List[Point]
        :rtype: int
        """
        if not points:
            return 0
        if len(points) <= 2:
            return len(points)
        # 想法很简单就是求每两点间的slope
        res = 0 
        for p in points:
            m = {}
            duplicate = 1
            vertical = 0
            for p1 in points:
                if p != p1:
                    if p.x == p1.x and p.y == p1.y:
                        duplicate += 1
                    elif p.x == p1.x:
                        vertical += 1
                    else:
                        slope = (p1.y - p.y) * np.longdouble(1) / (p1.x - p.x)
                        m[slope] = m.get(slope, 0) + 1
            print m
            res = max(res, vertical+duplicate)
            if m:
                res = max(res, max(m.values())+duplicate)
        return res