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

这道题做的时候要考虑几个edge 

1. infinity

2. same points

这里我们用hashtable将得到的slope存起来，最后每过一个点将其和其他所有点的组合成的slope数量进行比较最后得到最大值。

算法复杂度是o(n^2) 空间复杂度是O(n)

代码如下：

# Definition for a point
# class Point:
#     def __init__(self, a=0, b=0):
#         self.x = a
#         self.y = b

class Solution:
    # @param points, a list of Points
    # @return an integer
    def maxPoints(self, points):
        #slop={}
        maxp=0
        if len(points)<3:
            return len(points)
        for i in range(len(points)):
            samepoint=1
            slope={'inf':0}
            for j in range(len(points)):
                if i==j:
                    continue
                elif points[i].x==points[j].x and points[i].y==points[j].y:
                    samepoint+=1
                elif points[i].x==points[j].x and points[i].y!=points[j].y:
                    slope['inf']+=1
                else:
                    k=1.0*(points[i].y-points[j].y)/(points[i].x-points[j].x)
                    if k not in slope:
                        slope[k]=1
                    else:
                        slope[k]+=1
            maxp=max(maxp,max(slope.values())+samepoint)
        return maxp
       
        

Max Points on a Line Leetcode Python