題目及思路：

代碼:

#include <stdio.h>
#include <string.h>

int isLeapYear(int x){//1代表閏年 
    if( (x%4==0 && x%100!=0) || x%400==0) return 1;
    return 0;
}

int dayOfMonth[13][2]{
    0,0,
    31,31,
    28,29,
    31,31,
    30,30,
    31,31,
    30,30,
    31,31,
    31,31,
    30,30,
    31,31,
    
 
30,30,
    31,31
};
struct Date{
    int day;
    int month;
    int year;
    
    void nextDay(){
        day++;
        if( day > dayOfMonth[month][isLeapYear(year)]){
            day=1;
            month++;
            if(month > 12){
                month=1;
                year++;
            }
        }
    }
};

 
int buf[3001][13][32];//保存天數 
char monthName[13][20]{//月名 
    "",
    "January",
    "February",
    "March",
    "April",
    "May",
    "June",
    "July",
    "August",
    "September",
    "October",
    "November",
    "December"
} ;
char weekName[7][20]{//周名 
    "Sunday",
    "Monday",
    "Tuesday",
    
 
"Wednesday",
    "Thursday",
    "Friday",
    "Saturday"
};
int abs(int x){
    if(x < 0) return -x;
    return x;
}
int main(){
    Date time;
    time.day=1;
    time.month=1;
    time.year=1000;
    int cnt=0;//記錄天數
    while(time.year!=3001) {
        buf[time.year][time.month][time.day]=cnt;
        time.nextDay();
        cnt++;
    }
    int d,m,y;
    char s[20];
    while( scanf("%d%s%d",&d,&s,&y)!= EOF){
        for(m=1;m<=12;m++){    //得出月數 
            if(strcmp(s,monthName[m])==0)
                break;
        }
        int days=abs( buf[y][m][d] - buf[2018][1][8])+1;
        printf("%s\n",weekName[days%7]);
    }
    return 0;
}

日期類問題-判斷星期幾