【leetcode】1185.一周中的第几天

char * dayOfTheWeek(int day, int month, int year){
    int i,j,days=0;
    char* weeks[]={"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
    int monthArr[]={0,31,59,90,120,151,181,212,243,273,304,334,365};
    for(i=1971; i<year; i++){
        days+=365;
        if(i%4==0 && i%100 || i%400==0)
            days++;
    }
    days+=monthArr[month-1];
    if((year%4==0 && year%100 || year%400==0) && month>2)
        days++;
    days+=day;
    //1970年12月31日星期四
    return weeks[(4+days%7)%7];
}