LeetCode知识点总结 - 812

LeetCode 812. Largest Triangle Area

考点	难度
Array	Easy

题目

Given an array of points on the X-Y plane points where points[i] = [xi, yi], return the area of the largest triangle that can be formed by any three different points. Answers within 10^-5 of the actual answer will be accepted.

思路

把每一种选择组成的三角形面积都算一遍，选最大的。三角形面积的公式算法：https://www.mathopenref.com/coordtrianglearea.html

答案

public double largestTriangleArea(int[][] p) {
        double res = 0;
        for (int[] i: p)
            for (int[] j: p)
                for (int[] k: p)
            res = Math.max(res, 0.5 * Math.abs(i[0] * j[1] + j[0] * k[1] + k[0] * i[1]- j[0] * i[1] - k[0] * j[1] - i[0] * k[1]));
        return res;
}