UVa 150 - Double Time

Accepted date: 2015-11-11
Ranking (as of 2015-11-11): 2 out of 452
Language: C++

/*
  UVa 150 - Double Time

  To build using Visual Studio 2012:
    cl -EHsc -O2 UVa_150_Double_Time.cpp
*/

#include <cstdio>
#include <cstring>

const int nr_chars_max = 15, nr_days_of_week = 7, nr_months = 12;

const char* day_names[nr_days_of_week] = {
  "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
};

const char* month_names[nr_months] = {
  "January", "February", "March", "April", "May", "June",
  "July", "August", "September", "October", "November", "December"
};

int nr_days[2][nr_months] = {
  {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
  {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31} // leap year
};

int nr_days_of_year[2][nr_months] = {
  {31, 59, 90,120,151,181,212,243,273,304,334,365},
  {31, 60, 91,121,152,182,213,244,274,305,335,366} // leap year
};

const int start_year = 1582, start_day_of_week = 5 /* Friday */,
  julian_calendar_start_days = 273 + 5 /* 5 October */,
  gregorian_calendar_start_days = 273 + 15 /* 15 October */;

int get_day_of_week(const char* day)
{
  for (int i = 0; i < nr_days_of_week; i++)
    if (!strcmp(day, day_names[i]))
      return i;
  return -1;
}

int get_month(const char* month)
{
  for (int i = 0; i < nr_months; i++)
    if (!strcmp(month, month_names[i]))
      return i;
  return -1;
}

bool julian_calendar_leap_year(int year)
{
  return !(year % 4);
}

int julian_calendar_number_of_leap_years(int syear, int eyear)
{
  // number of leap years between [syear, eyear)
  syear--; eyear--;
  return eyear / 4 - syear / 4;
}

int julian_calendar_number_of_days(int year, int month, int day)
{
  int nr_days = (year - start_year) * 365 +
    julian_calendar_number_of_leap_years(start_year, year) -
    julian_calendar_start_days;
  int leap_year = julian_calendar_leap_year(year) ? 1 : 0;
  if (month)
    nr_days += nr_days_of_year[leap_year][month - 1];
  nr_days += day;
  return nr_days;
}

bool gregorian_calendar_leap_year(int year)
{
  if (!(year % 400))
    return true;
  else if (!(year % 100))
    return false;
  else if (!(year % 4))
    return true;
  else
    return false;
}

int gregorian_calendar_number_of_leap_years(int syear, int eyear)
{
  // return the number of leap years between [syear, eyear)
  syear--; eyear--;
  return (eyear / 4 - eyear / 100 + eyear / 400) -
    (syear / 4 - syear / 100 + syear / 400);
}

int gregorian_calendar_number_of_days(int year, int month, int day)
{
  int nr_days = (year - start_year) * 365 +
    gregorian_calendar_number_of_leap_years(start_year, year) -
    gregorian_calendar_start_days;
  int leap_year = gregorian_calendar_leap_year(year) ? 1 : 0;
  if (month)
    nr_days += nr_days_of_year[leap_year][month - 1];
  nr_days += day;
  return nr_days;
}

int main()
{
  while (true) {
    int day_of_week, day, month, year, leap_year, j_days, g_days;
    char day_name[nr_chars_max + 1], month_name[nr_chars_max + 1];
    scanf("%s", day_name);
    if (day_name[0] == '#')
      break;
    scanf("%d %s %d", &day, month_name, &year);
    day_of_week = get_day_of_week(day_name), month = get_month(month_name);
    j_days = julian_calendar_number_of_days(year, month, day);
    if ((start_day_of_week + j_days) % nr_days_of_week == day_of_week) {
      // julian calendar
      g_days = j_days + gregorian_calendar_start_days;
      for (year = start_year; ; year++) {
        leap_year = gregorian_calendar_leap_year(year) ? 1 : 0;
        if (g_days <= nr_days_of_year[leap_year][nr_months - 1])
          break;
        g_days -= nr_days_of_year[leap_year][nr_months - 1];
      }
      for (month = 0; ; month++) {
        if (g_days <= nr_days[leap_year][month])
          break;
        g_days -= nr_days[leap_year][month];
      }
      printf("%s %d %s %d\n", day_name, g_days, month_names[month], year);
    }
    else { // gregorian calendar
      g_days = gregorian_calendar_number_of_days(year, month, day);
      j_days = g_days + julian_calendar_start_days;
      for (year = start_year; ; year++) {
        leap_year = julian_calendar_leap_year(year) ? 1 : 0;
        if (j_days <= nr_days_of_year[leap_year][nr_months - 1])
          break;
        j_days -= nr_days_of_year[leap_year][nr_months - 1];
      }
      for (month = 0; ; month++) {
        if (j_days <= nr_days[leap_year][month])
          break;
        j_days -= nr_days[leap_year][month];
      }
      printf("%s %d* %s %d\n", day_name, j_days, month_names[month], year);
    }
  }
  return 0;
}