[LeetCode]题解（python）：149-Max Points on a Line

题目来源：

　　https://leetcode.com/problems/max-points-on-a-line/

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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。

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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。

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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