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构造一个矩形类Rectangle，数据成员为矩形的左下角与右上角的坐标，并利用成员函数实现对矩形周长与面积的计算

#include <iostream>

class Rectangle
{
public:
    Rectangle(double x1, double y1, double x2, double y2) : _x1(x1), _y1(y1), _x2(x2), _y2(y2) {}

    double perimeter() const
    {
        return std::abs(_x1 - _x2) * 2.0 + std::abs(_y1 - _y2) * 2.0;
    }

    double area() const
    {
        return std::abs(_x1 - _x2) * std::abs(_y1 - _y2);
    }

private:
    double _x1;
    double _y1;
    double _x2;
    double _y2;
};

int main()
{
    double x1, y1, x2, y2;
    std::cout << "输入左下角坐标: ";
    std::cin >> x1 >> y1;
    std::cout << "输入右上角坐标: ";
    std::cin >> x2 >> y2;
    Rectangle r(x1, y1, x2, y2);
    std::cout << "周长: " << r.perimeter() << std::endl;
    std::cout << "面积: " << r.area() << std::endl;
    return 0;
}

#include <iostream>
#include <math.h>
using namespace std;
class Rectangle
{
public:
    double x, y;   //左下
    double _x, _y; //右上
    Rectangle(double x, double y, double _x, double _y)
    {
        this->x = x;
        this->y = y;
        this->_x = _x;
        this->_y = _y;
    }
    void p()
    {
        cout << "周长:" << 2 * fabs(x - _x) + 2 * fabs(y - _y) << endl;
    }
    void area()
    {
        cout << "面积:" << fabs(x - _x) * fabs(y - _y) << endl;
    }
};
int main(void)
{
    double x, y;
    double _x, _y;
    cout << "输入左下坐标(x,y):";
    cin >> x >> y;
    cout << "输入右上坐标(_x,_y):";
    cin >> _x >> _y;
    Rectangle rec(x, y, _x, _y);
    rec.p();
    rec.area();
    return 0;
}

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
class printS {
public:
    float x; float y;
};
class Rectangle {
public:
    printS pointA;
    printS pointB;
    float zc() {
        float length = 0;
        float width = 0;
        if (pointA.x>pointB.x)
        {
            width = pointA.x - pointB.x;
        }
        else
        {
            width = pointB.x - pointA.x;
        }
        if (pointA.y > pointB.y)
        {
            length = pointA.y - pointB.y;
        }
        else
        {
            length = pointB.y - pointA.y;
        }
        return 2 * (width + length);
    }
    float mj() {
        float length = 0;
        float width = 0;
        if (pointA.x > pointB.x)
        {
            width = pointA.x - pointB.x;
        }
        else
        {
            width = pointB.x - pointA.x;
        }
        if (pointA.y > pointB.y)
        {
            length = pointA.y - pointB.y;
        }
        else
        {
            length = pointB.y - pointA.y;
        }
        return length * width;
    }
};
int main()
{
    float x1, y1,x2,y2;
    Rectangle* rec = (Rectangle*)malloc(sizeof(Rectangle));
    printf("输入左下角坐标（用空格隔开）：");
    scanf("%f%f",&x1,&y1);
    printf("输入右上角坐标（用空格隔开）：");
    scanf("%f%f", &x2, &y2);
    rec->pointA.x = x1;
    rec->pointA.y = y1;
    rec->pointB.x = x2;
    rec->pointB.y = y2;
    printf("矩形面积是：%f",rec->mj());
    printf("矩形周长是：%f", rec->zc());
    return 0;
}