用C++编程计算图形面积

以下是使用 C++ 编写的计算图形面积的示例程序，其中计算了圆、矩形和三角形的面积：

#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    int choice;
    float area;

    cout << "Choose a shape to calculate its area:\n";
    cout << "1. Circle\n";
    cout << "2. Rectangle\n";
    cout << "3. Triangle\n";
    cin >> choice;

    switch(choice)
    {
        case 1:
        {
            float radius;
            cout << "Enter the radius of the circle: ";
            cin >> radius;

            area = M_PI * pow(radius, 2);
            cout << "The area of the circle is: " << area;
            break;
        }

        case 2:
        {
            float length, width;
            cout << "Enter the length and width of the rectangle: ";
            cin >> length >> width;

            area = length * width;
            cout << "The area of the rectangle is: " << area;
            break;
        }

        case 3:
        {
            float base, height;
            cout << "Enter the base and height of the triangle: ";
            cin >> base >> height;

            area = 0.5 * base * height;
            cout << "The area of the triangle is: " << area;
            break;
        }

        default:
            cout << "Invalid choice";
    }

    return 0;
}

在此程序中，我们使用 `switch` 语句根据用户选择的形状来计算面积。根据所选的形状，程序会要求用户输入所需的参数（如圆的半径、矩形的长度和宽度等），并使用相应的公式计算面积。最后，程序将计算出的面积输出到屏幕上。