USACO section 1.1 Friday the Thirteenth

这道题挺不好写的，题目是说给出一个年份范围，统计这个范围内星期一到星期日为 13 号的个数。

/*

PROG: friday

LANG: C++

*/

# include <cstdio>



const char daytab[2][13] = {

    {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},

    {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

};



int isLeap(int year)

{

    return year%4 == 0 && year%100 != 0 || year%400 == 0 ? 1 : 0;

}



int dayOfMonth(int year, int day)

{

    int leap, i;

    leap = isLeap(year);

    for (i = 1; day > daytab[leap][i]; ++i)

        day -= daytab[leap][i];

    return day;

}



int main()

{

    int n;



    freopen("friday.in", "r", stdin);

    freopen("friday.out", "w", stdout);



    scanf("%d", &n);

    int f[7];

    for (int i = 0; i < 7; ++i)

        f[i]  = 0;

    int day = 0, wk = 0;

    for (int year = 1900; year < 1900+n; )

    {

        wk = (wk+1) % 7;

        ++day;

        if (dayOfMonth(year, day) == 13) ++f[wk];

        if ((day == 365 && isLeap(year) == 0) || (day == 366 && isLeap(year) == 1))

        {

            ++year;

            day = 0;

        }

    }

    printf("%d", f[6]);

    for (int i = 0; i < 6; ++i)

        printf(" %d", f[i]);

    printf("\n");



    fclose(stdin);

    fclose(stdout);



    return 0;

}

/**/