getchar(),gets()

最重要的区别是gets读一行，getchar()()读一个字符。

先看原型：
char() * gets(char() * ptr);
int getchar(void);

作用是：

gets()用于从标准输入流stdin读入一个整行（以'\n'或EOF）结束，写入ptr指向的字符数组，并返回这个指针；出错或遇到文件结束时则返回NULL。行末的'\n'从流中取出，但不写入数组。gets()不检查被写入的数组大小。

getchar()用于从标准输入流stdin读入一个字符，并返回这个字符。如果读到文件结尾，则返回EOF。注意到EOF不能用char类型表示，所以getchar()函数返回的是一个int型的数。使用时也应该注意这一点。

 

#include<stdio.h>
#include<stdlib.h>
int main()
{
    system("color f5");
    printf("     *\n    **\n     ***\n");
    system("pause");
    return 0;
}

 

#include<iostream>
#include<math.h>
using namespace std;

class Shape
{
public:
    virtual double Area() const = 0;
    virtual double Perim() const = 0;
    virtual void Show()
	{
		cout << "Area is:" << Area() << endl;
        cout << "Perim is:" << Perim() << endl;
	}
};

class Rectangle:public Shape
{
private:
    double Length;
    double Width;
public:
    Rectangle(double Length = 0,double Width = 0)
    {
        this->Length = Length;
        this->Width = Width;
    }

    ~Rectangle()
    {

    }
    double Area() const
    {
        return Length*Width;
    }

    double Perim() const
    {
        return 2*(Length+Width);
    }

    /*void Show( )
    {
        cout << "Area is:" << Area() << endl;
        cout << "Perim is:" << Perim() << endl;
    }*/
};

const double PI = 3.14159;
class Circle:public Shape
{
private:
    double Radius;
public:
    Circle(double Radius = 0)
    {
        this->Radius = Radius;
    }

    ~Circle()
    {

    }
    double Area()const
    {
        return PI*Radius*Radius;
    }

    double Perim() const
    {
        return 2*PI*Radius;
    }

    /*void show()
    {
        cout << "Area is:" << Area() << endl;
        cout << "Perim is:" << Perim() << endl;
    }*/
};

class Triangle:public Shape
{
private:
    double A,B,C;
public:
    Triangle(double A = 0,double B = 0,double C = 0)
    {
        this->A = A;
        this->B = B;
        this->C = C;
    }

    ~Triangle()
    {

    }

    double Area() const
    {
        double P;
        P = (A +B + C)/2;
        return sqrt(P*(P-A)*(P-B)*(P-C));
    }

    double Perim() const
    {
        return(A+B+C);
    }

    /*void show()
    {
        cout << "Area is:" << Area() << endl;
        cout << "Perim is:" << Perim() << endl;
    }*/

};

void main()
{
    double Length,Width,Radius,A,B,C;
    cout << "Rectangle :" << endl;
loopa:
    cout << "请输入矩形的长河宽(Length,Width):" << endl;
    cin >> Length >> Width;
    if(Length <= 0||Width <= 0)
    {
        cout << "输入的长度不能构成一个矩形!请重新输入!" <<endl;
        goto loopa;
    }
    else
    {
        Rectangle Rect(Length,Width);
        Rect.Show();
        cout << "Circle: "<<endl;
    }

loopb:
    cout << "请输入圆形的半径(Radius): " << endl;
    cin >> Radius;
    if(Radius <= 0)
    {
        cout << "输入的半径不能构成一个圆!请重新输入!" << endl;
        goto loopb;

    }
    else
    {
        Circle Cir(Radius);
        Cir.Show();
        cout << "Triangle:" << endl;
    }

loopc:
    cout << "请输入三角形的三边(A,B,C): "<< endl;
    cin >> A >> B >> C;
    if(A <= 0||B <= 0||C <= 0 ||(A+B) <= C || (A + C) <= B||(B + C) <= A)
    {
        cout << "输入的三边值不能构成一个三角形!请重新输入!" << endl;
        goto loopc;
    }
    else
    {
        Triangle Tri(A,B,C);
        Tri.Show();
    }
}