C++作业3.5

一求圆面积（cout控制符）
tream.h>
#include<iomanip.h>
const float PI =3.14159;
void main ()
{
float s,l,r;
cout<<"Please input r:";
cin>>r;
s=PI*r*r;
l=2*PI*r;
cout<<"r="<<r<<setw(5)<<"s="<<s<<setw(5)<<"1="<<l
<<endl;
cout<<"r="<<setiosflags(ios::scientific)<<r<<setw(5)<<"s="<<s<<setw(5)<<"1="<<l<<endl; }
二求矩形面积（scanf printf）
#include<stdio.h>
void main()
{
int a,b;
float d;
scanf("%d %d",&a,&b);
scanf("(%d+%d)*2=%d\n",a,b,(a+b)*2);
scanf("(%d*%d)=%d\n",a,b,a*b);
printf("此长方形周长为:");
printf("%d\n\n",(a+b)*2);
printf("此长方形面积为:");
printf("%d\n",a*b);
}
三求分段函数书P70,5.1
#include <stdio.h>
#include<iostream.h>
void main()
{
int x,y;
cout<<"请输入X的值"<<endl;
cin>>x;
if(x<5)
y=x;
else if(x<15)
y=x+6;
else if(x>=15)
y=x-6;
cout<<"y的值为:"<<y<<endl;
}
四鞋子营销
#include<iostream.h>
void main()
{
int x,y,n,m;
cout<<" "<<"***************"<<endl;
cout<<" "<<"*"<<" 欢迎光临*"<<endl; cout<<" "<<"*"<<" 一双鞋100元*"<<endl; cout<<" "<<"*"<<" 买二送一*"<<endl; cout<<" "<<"***************"<<endl;
cout<<"请输入购买金额"<<endl;
cin>>x;
n=x/100;
y=n/2;
n=n+y;
if(x<100)
cout<<"对不起，您不能买鞋！";
else
cout<<"您可以买"<<n<<"双鞋"<<endl;
五三数字a,b,c比大小
#include<iostream.h>
void main()
{
int a,b,c,t;
cout<<"请输入3个数字"<<endl;
cin>>a>>b>>c;
if(a>b)
{
t=a;
a=b;
b=t;
}
if(a>c)
{
t=a;
a=c;
c=t;
}
if(b>c)
{
t=b;
b=c;
c=t;
}
cout<<"这3个数字从小到大排列依次为："<<endl; cout<<a<<"<"<<b<<"<"<<c<<endl;
}。