c++第三次作业

#include <iostream>
using namespace std;
int main()
{
int year,month;
cout<<"输入年份和月份：";
cin>>year>>month;
{
if(month==2)
{
if(year%4==0||year%100==0) cout<<29;
else cout<<28;
}
else
if(month==1||3||5||7||8||10||12) cout<<31;
else cout<<30;
}
return 0;
}

#include <iostream>
using namespace std;
int main()
{
float l,j,n,c;
char d;
cout<<"欢迎使用利息计算器\n请输入存款金额"<<endl;
cin>>j;
cout<<"存款期限”<<endl<<1.三个月<<endl<<b.六个月<<endl<<3.一年<<endl<<4.两年<<endl<<5.三年<<endl<<6.五年<<endl<<请输入存款期限的代号：";
cin>>d;
l=j*n*c;
switch(d)
{
case 1:c==0.25,n==0.031;break;
case 2:c==0.5,n==0.033;break;
case 3:c==1,n==0.035;break;
case 4:c==2,n==0.044;break;
case 5:c==3,n==0.05;break;
case 6:c==5,n==0.055;break;
defalut:cout<<"发生错误";
}
cout<<l;

}

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
double x,y;
cin>>x;
if(x<2) y=x;
else
if(x>=2&&x<6) y=x*x+1;
else
if(x>=6&&x<10) y=sqrt(x+1);
else y=1/(x+1);
cout<<y;
return 0;
}