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;
}

/**/