31.假定2007年的一月一日是星期一，输入一个时间（包含年、月、日），求出它是星期几。

#include<iostream>
using namespace std;

int main()
{
    int y,m,d,temp;
    int a[]={0,31,28,31,30,31,30,31,31,30,31,30,31};
    int TotalDay=365;
    int sum=0,sum1=0,sum2=0;


    cout<<"if 2007.1.1 is Monday,please input a date,i can figure out what day it is:"<<endl;
    cin>>y>>m>>d;


    for(int i=2007;i<y;i++)
    {
        if((i%4==0)&&(i%100!=0)||(i%400==0))
        {
            TotalDay+=1;
        }
        sum1+=TotalDay;
    }

    if((y%4==0)&&(y%100!=0)||(y%400==0))
    {
        a[2]+=1;
        for(int i=1;i<m;i++)
        {
            sum2+=a[i];
        }
        sum=sum1+sum2+d;
    }else
    {
        for(int j=1;j<m;j++)
        {
            sum2+=a[j];
        }
        sum=sum1+sum2+d;
    }
    temp=sum%7;
    switch(temp)
    {
        case 0 : cout<<"Monday";break;
        case 1 : cout<<"Tuesday";break;
        case 2 : cout<<"Wednesday";break;
        case 3 : cout<<"Thursday";break;
        case 4 : cout<<"Friday";break;
        case 5 : cout<<"Saturday";break;
        case 6 : cout<<"Sunday";break;
        default : break;
    }
    return 0;
}