c++第3次作业

#include<iostream>
using namespace std;
int main()
{
int dYear,dMonth,dDay;
cout<<"请输入年份和月份：";
cin>>dYear>>dMonth;
if(dYear%4==0 && dYear%400==0)
{
switch(dMonth)
{

case 1: dDay=31;
case 2: dDay=29; break;
case 3: dDay=31; break;
case 4: dDay=30; break;
case 5: dDay=31; break;
case 6: dDay=30; break;
case 7: dDay=31; break;
case 8: dDay=31; break;
case 9: dDay=30; break;
case 10: dDay=31; break;
case 11: dDay=30; break;
case 12: dDay=31; break;
}

}
else
{
switch(dMonth)
{
case 1: dDay=31;
case 2: dDay=28; break;
case 3: dDay=31; break;
case 4: dDay=30; break;
case 5: dDay=31; break;
case 6: dDay=30; break;
case 7: dDay=31; break;
case 8: dDay=31; break;
case 9: dDay=30; break;
case 10: dDay=31; break;
case 11: dDay=30; break;
case 12: dDay=31; break;
}
}
cout<<"本月"<<dDay<<"天。"<<endl;
return 0;
}

#include<iostream>
using namespace std;
int main()
{
double dRate,dTerm,dIncome,dInterest=0;//dRate为年利率，dTerm为存期，dInterest为利息
int x,dMoney;
cout<<"欢迎使用利息计算器！\n"<<"请输入存款金额：";
cin>>dMoney;
cout<<"======存款期限======\n"<<"1. 三个月\n"<<"2. 六个月\n"<<"3. 一年\n"<<"4. 两年\n"<<"5. 三年\n"<<"6. 五年\n";
cout<<"请输入存款期限的代号："<<endl;
cin>>x;
switch(x)
{
case 1:  dRate=0.031, dTerm=0.25;  break;
case 2:  dRate=0.033, dTerm=0.5;  break;
case 3:  dRate=0.035, dTerm=1;  break;
case 4:  dRate=0.044, dTerm=2;  break;
case 5:  dRate=0.050, dTerm=3;  break;
case 6:  dRate=0.055, dTerm=5;  break;
}
dInterest=dMoney*dRate*dTerm;
dIncome=dInterest+dMoney;
cout<<"到期利息为："<<dInterest<<"元，"<<"本息合计共："<<dIncome<<"元。\n";
cout<<"感谢你的使用，欢迎下次光临！"<<endl;
return 0;
}

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