给定n个点及xy坐标求出用任意三个点围成的三角形面积总和保留1位小数 n=3000;xiyi∈-1000010000例：输入：50 11 01 12 11 2输出：60C++实现

#include <iostream>
#include <vector>
#include <cmath>
using namespace std;

double getTriangleArea(double x1, double y1, double x2, double y2, double x3, double y3) {
    return abs(x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2)) / 2.0;
}

double getSumOfTriangleAreas(vector<pair<double, double>>& points) {
    double sum = 0.0;
    int n = points.size();
    for (int i = 0; i < n - 2; i++) {
        for (int j = i + 1; j < n - 1; j++) {
            for (int k = j + 1; k < n; k++) {
                double x1 = points[i].first;
                double y1 = points[i].second;
                double x2 = points[j].first;
                double y2 = points[j].second;
                double x3 = points[k].first;
                double y3 = points[k].second;
                sum += getTriangleArea(x1, y1, x2, y2, x3, y3);
            }
        }
    }
    return sum;
}

int main() {
    int n;
    cin >> n;
    vector<pair<double, double>> points(n);
    for (int i = 0; i < n; i++) {
        cin >> points[i].first >> points[i].second;
    }
    double sum = getSumOfTriangleAreas(points);
    cout << fixed << sum << endl;
    return 0;
}
``