用c++编写挖方填方代码，使用dem数据

好的，挖方填方是一种常见的土木工程计算，可以使用DEM（数字高程模型）数据进行计算。下面是一个简单的C++程序示例，用于计算给定DEM数据中的挖方和填方量：

#include <iostream>
#include <fstream>
#include <cmath>

using namespace std;

const double PI = 3.14159265358979323846;

// 计算面积
double calcArea(double x1, double y1, double x2, double y2, double x3, double y3) {
    return 0.5 * abs((x1 - x3) * (y2 - y3) - (x2 - x3) * (y1 - y3));
}

// 计算三角形的高
double calcHeight(double x1, double y1, double x2, double y2, double x3, double y3) {
    double area = calcArea(x1, y1, x2, y2, x3, y3);
    double edge = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
    return 2 * area / edge;
}

// 计算挖方和填方量
void calcVolume(double** data, int rows, int cols, double height) {
    double volume = 0;
    for (int i = 0; i < rows - 1; i++) {
        for (int j = 0; j < cols - 1; j++) {
            double x1 = j, y1 = i, z1 = data[i][j];
            double x2 = j + 1, y2 = i, z2 = data[i][j + 1];
            double x3 = j, y3 = i + 1, z3 = data[i + 1][j];
            double x4 = j + 1, y4 = i + 1, z4 = data[i + 1][j + 1];
            double h1 = max(0.0, height - z1);
            double h2 = max(0.0, height - z2);
            double h3 = max(0.0, height - z3);
            double h4 = max(0.0, height - z4);
            double v1 = h1 * calcArea(x1, y1, x2, y2, x3, y3);
            double v2 = h2 * calcArea(x2, y2, x4, y4, x3, y3);
            double v3 = h3 * calcArea(x1, y1, x3, y3, x4, y4);
            double v4 = h4 * calcArea(x2, y2, x4, y4, x1, y1);
            volume += (v1 + v2 + v3 + v4) / 4;
        }
    }
    if (volume > 0) {
        cout << "填方量: " << volume << endl;
    }
    else {
        cout << "挖方量: " << -volume << endl;
    }
}

int main() {
    ifstream fin("dem.txt");
    int rows, cols;
    double** data;
    fin >> rows >> cols;
    data = new double*[rows];
    for (int i = 0; i < rows; i++) {
        data[i] = new double[cols];
        for (int j = 0; j < cols; j++) {
            fin >> data[i][j];
        }
    }
    fin.close();
    double height;
    cout << "请输入高度: ";
    cin >> height;
    calcVolume(data, rows, cols, height);
    for (int i = 0; i < rows; i++) {
        delete[] data[i];
    }
    delete[] data;
    return 0;
}

以上代码读取了一个名为“dem.txt”的DEM数据文件，该文件第一行包含行数和列数，接下来的每一行包含一系列高程数据。程序提示用户输入高度，然后计算挖方和填方量。