【leetcode刷题】T214-最大三角形面积

示例:
输入: points = [[0,0],[0,1],[1,0],[0,2],[2,0]]
输出: 2
解释: 
这五个点如下图所示。组成的橙色三角形是最大的，面积为2。

class Solution(object):
    def largestTriangleArea(self, points):
        """
        :type points: List[List[int]]
        :rtype: float
        """
        length = len(points)
        res = 0
        for i in range(length):
            p1 = points[i]
            for j in range(i+1, length):
                p2 = points[j]
                for k in range(j+1, length):
                    p3 = points[k]
                    s = abs(p1[0] * (p2[1] - p3[1]) + p2[0] * (p3[1] - p1[1]) + p3[0] * (p1[1] - p2[1])) / 2.0
                    res = max(s, res)
        return res