Euler19 - 10min to lose...

euler.cpp

#include <iostream>
#include <string>
#include <vector>

enum yearTypeT
{
    COMMON = 0, LEAP
};

using yearT = unsigned int;

enum monthT
{
    JAN = 0, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC, NB_MONTH_IN_YEAR
};

enum dayT
{
    MON = 0, TUE, WED, THU, FRI, SAT, SUN, NB_DAY_IN_WEEK
};

unsigned int isLeapYear(yearT year)
{
    if (year%4 != 0)
        return COMMON;
    else if (year%100 != 0)
        return LEAP;
    else if (year%400 != 0)
         return COMMON;
    else
        return LEAP;
}

unsigned int nbDaysInYear(yearT year)
{
    return 365 + isLeapYear(year);
}

unsigned int nbDaysInMonth(monthT month, yearT year)
{
    unsigned int res;
    switch(month)
    {
        case APR :
        case JUN :
        case SEP : 
        case NOV : res = 30; break;
        case FEB : res = 28 + isLeapYear(year); break;
        default : res = 31;
    }
    return res;
}

int main()
{
    auto res = 0;
    
    unsigned int currentDay = MON; //1 Jan 1900 was a Monday
    currentDay = (currentDay + nbDaysInYear(1900)) % NB_DAY_IN_WEEK; // Day of 1 Jan 1901
    
    for(yearT year = 1901; year <= 2000; ++year)
    {
        for(monthT month = JAN; month <= DEC; month=monthT(month+1) )
        {
            currentDay = (currentDay + nbDaysInMonth(month, year)) % NB_DAY_IN_WEEK;
            if (currentDay==SUN) 
                res++;
        }
    }
    std::cout << res;
}