Largest Triangle Area

给一个点的数组, 求最大的三角形, 这个题要是不知道 https://en.wikipedia.org/wiki/Shoelace_formula , 基本没法做.

class Solution {
    public double largestTriangleArea(int[][] points) {
        double res = 0;
        for (int i = 0; i < points.length; i++)
            for (int j = i+1; j < points.length; j++)
                for (int k = j+1; k < points.length; k++)
                    res = Math.max(res, area(points[i], points[j], points[k]));
        return res;
    }

    public double area(int[] P, int[] Q, int[] R) {
        return 0.5 * Math.abs(P[0]*Q[1] + Q[0]*R[1] + R[0]*P[1]
                             -P[1]*Q[0] - Q[1]*R[0] - R[1]*P[0]);
    }
}