add: 220515-CN [cpp]

cpp/2205/220515-CN.cpp

@@ -0,0 +1,22 @@
+#include <vector>
+
+/**
+ * 812. Largest Triangle Area
+ * 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.
+ */
+
+class Solution {
+public:
+	static double largestTriangleArea(std::vector<std::vector<int>>& points) {
+		const int n = points.size();
+		double ret = 0.0;
+		for (int i = 0; i < n; ++i) {
+			for (int j = 1 + i; j < n; ++j) {
+				for (int k = 1 + j; k < n; ++k) {
+					ret = std::max(ret, 0.5 * abs(points[i][0] * points[j][1] + points[j][0] * points[k][1] + points[k][0] * points[i][1] - points[i][0] * points[k][1] - points[j][0] * points[i][1] - points[k][0] * points[j][1]));
+				}
+			}
+		}
+		return ret;
+	}
+};