这道题难度不大，就是比较麻烦。求解所有月份13号是星期几。

 

#include 
     
       #include 
      
        #include 
       
         #include 
        
          using namespace std; const int MONTHS[] = {
   0,31,28,31,30,31,30,31,31,30,31,30,31}; vector
         
           ACC_MONTHS(13,0); vector
          
            ACC_LEAP_MONTHS(13,0); bool is_leap_year(int year); void accumulate_months(vector
           
             &acc_months,bool is_leap){ int count=0; for(int i=0;i<=12;i++){ int days = MONTHS[i]; if(i==2&&is_leap) days+=1; count+=days; acc_months[i] = count; } } int first_day_of_year(int year){ int d=0; for(int i=1901;i<=year;++i){ int days = 365; if(is_leap_year(i-1)) days=366; d = (d+days)%7; } return d; } int weekday(int year,int month,int day,int first_day){ vector
            
              *acc_months = &ACC_MONTHS; if(is_leap_year(year)) acc_months = &ACC_LEAP_MONTHS; return ((*acc_months)[month-1]+day-1+first_day)%7; } bool is_leap_year(int year){ if(year%400==0) return true; else if( (year%4==0) && (year%100!=0) ) return true; else return false; } void solve(int N, vector
             
               &stat){ for(int i =1900;i<1900+N;++i){ int first_day = first_day_of_year(i); //cout<
              <<":"<
               
                <
                
                 >N; //stat:start from monday(0) to Sunday(6) vector
                 
                   stat(7,0); solve(N,stat); for(int i=0;i<7;++i){ fout<