题目来源：
https://leetcode.com/problems/max-points-on-a-line/
题意分析：
在一个2D的板上面有很多个点，判断最多有多少个点在同一条直线上。
题目思路：
这里我们可以用斜率来记录两条边是否在同一条直线。如果考虑再细一点，由于double有精度的问题，斜率最后用分数来表示。
代码（python）：
# Definition for a point.
# class Point(object):
# def __init__(self, a=0, b=0):
# self.x = a
# self.y = b class Solution(object):
def maxPoints(self, points):
"""
:type points: List[Point]
:rtype: int
"""
size = len(points)
if size < 3:
return size
ans = 0
for i in range(size):
d = {'inf':0}
samePoint = 1
for j in range(size):
if i == j:
continue
elif points[i].x == points[j].x and points[i].y != points[j].y:
d['inf'] += 1
elif points[i].x != points[j].x:
k = 1.0 * (points[i].y - points[j].y) / (points[i].x - points[j].x)
if k in d:
d[k] += 1
else:
d[k] = 1
else:
samePoint += 1
ans = max(ans,max(d.values()) + samePoint)
return ans