[数据结构与算法]在C++中 结构体，枚举 结构的相关使用。事例。

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <sstream>
using namespace std;

struct Point3D{
    float x;
    float y;
    float z;

    Point3D()
    {
        x = 0; y = 0; z = 0;
    }

    Point3D(float x)
    {
        this->x = x; y = 0; z = 0;
    }

    Point3D(float x,float y,float z=0)
    {
        this->x = x;
        this->y = y;
        this->z = z;
    }
};

enum  EleType{TRI,QUD,TET,HEX};

struct Element {
    EleType elementType;
    Point3D nodes[8];

    Element(Point3D p0, Point3D p1, Point3D p2)
    {
        elementType = TRI;

        nodes[0].x = p0.x;
        nodes[1].x = p1.x;
        nodes[2].x = p2.x;
        nodes[0].y = p0.y;
        nodes[1].y = p1.y;
        nodes[2].y = p2.y;
    }

    Element(Point3D p0, Point3D p1, Point3D p2, Point3D p3)
    {
        elementType = QUD;
        nodes[0].x = p0.x;
        nodes[1].x = p1.x;
        nodes[2].x = p2.x;
        nodes[3].x = p3.x;
        nodes[0].y = p0.y;
        nodes[1].y = p1.y;
        nodes[2].y = p2.y;
        nodes[3].y = p3.y;
    }   
};

float distance(Point3D a, Point3D b)//两点之间的距离
{
    float d = 0;
    d = (a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y) + (a.z - b.z) * (a.z - b.z);
    return sqrt(d);
}

float tri_area(float a, float b, float c) //三角形面积
{
    return 1.0 / 4 * sqrt((a + b + c) * (a + b - c) * (a + c - b) * (b + c - a));
}

float area(Element E)
{
    float s = 0;
    float a, b, c, d,e;
    if (E.elementType == TRI)
    {
        a = distance(E.nodes[0], E.nodes[1]);
        b = distance(E.nodes[1], E.nodes[2]);
        c = distance(E.nodes[2], E.nodes[0]);
        s = tri_area(a,b,c);
    }

    if (E.elementType == QUD)
    {
        a = distance(E.nodes[0], E.nodes[1]);
        b = distance(E.nodes[1], E.nodes[2]);

        c = distance(E.nodes[2], E.nodes[0]);

        d = distance(E.nodes[0], E.nodes[3]);
        e = distance(E.nodes[2], E.nodes[3]);

        s = tri_area(a, b, c)+ tri_area(e, d, c);
    }


    return s;
}
int main()
{
    Point3D points[12] = {
        Point3D(20.,15.),
        Point3D(-15.,15.),
        Point3D(20.,-16.25),
        Point3D(-15.,-16.25),
        Point3D(-36.2392235,22.0970879),
        Point3D(-41.25,-10.),
        Point3D(-22.0970879,-36.2392235),
        Point3D(10.,-41.25),
        Point3D(36.2392235,-22.0970879),
        Point3D(41.25,10.),
        Point3D(22.0970879,36.2392235),
        Point3D(-10.,41.25)
    };
    for (int i = 0; i < 12; i++)
    {
        stringstream xx,yy;
        xx << points[i].x;
        yy << points[i].y;
        string x = xx.str();
        string y = yy.str();
        cout << i+1 << ",\t";
        cout << x << ",\t" << y << "\n";
    }
    Element elements[8] =
    {
        Element(points[10 - 1],points[11 - 1],points[1 - 1]),
        Element(points[8 - 1],points[9 - 1],points[3 - 1]),
        Element(points[6 - 1],points[7 - 1],points[4 - 1]),
        Element(points[12 - 1],points[5 - 1],points[1 - 1]),

        Element(points[12 - 1],points[2 - 1],points[1 - 1],points[11 - 1]),
        Element(points[2 - 1],points[5 - 1],points[6 - 1],points[4 - 1]),
        Element(points[4 - 1],points[7 - 1],points[8 - 1],points[3 - 1]),
        Element(points[3 - 1],points[9 - 1],points[10 - 1],points[1 - 1])
    };

    cout << "请输入单元编号[1-8]:";
    int n;
    cin >>  n;
    if (n < 1 || n>8)//非常输入退出
    {
        cout << "输入的的单元编号不存在~！" << endl;
        
    }
    else
    {
        cout << "单元编号为" << n << "图形面积是:" << area(elements[n - 1]) << endl;
    }
    float s = 0;
    for (int i = 0; i < 8; i++)
    {
        s += area(elements[i]);
    }

    cout << "8个单元编号的所有图形面积是:" << s << endl;
    return 0;
}

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