/* [Coding Challenge] Palindrome Date by Tibor Santa Today is 2nd February, 2020. It is special because it is a palindrome date: if we read the numbers backwards, we get the same result! Task: figure out all palindrome days since 2000 and predict the next few. * you may consider your local date format, or all/any of YYYYMMDD, DDMMYYYY, MMDDYYYY * don't forget about leap years */ #include #include #include #include using namespace std; auto is_leap = [](int year) { return !(year % 400) || (year % 100 && !(year % 4)); }; auto get_num_days = [](int yr, int month) { static int mdays[]{31,28,31,30,31,30,31,31,30,31,30,31}; return (is_leap(yr) && month == 1) ? mdays[month]+1 : mdays[month]; }; auto form_date = [](int d, int m, int y) { stringstream ss; ss << setw(2) << setfill('0') << d << setw(2) << setfill('0') << m+1 << y; return ss.str(); }; auto is_palindrome = [](auto&& dstr) { size_t sz = dstr.size()/2; return equal(dstr.begin(), dstr.begin()+sz, dstr.rbegin()); }; int main() { constexpr int syear {2000}; constexpr int eyear {3100}; cout << "All palindromic dates from 01-01-2000 to 31-12-3100 are:\n\n"; for(int yr = syear; yr <= eyear; ++yr) { for(int mon = 0; mon < 12; ++mon) { int ndays = get_num_days(yr,mon); for(int d = 1; d <= ndays; ++d) { auto dstr{form_date(d,mon,yr)}; if(is_palindrome(dstr)) { cout << dstr.substr(0,2) << " - " << dstr.substr(2,2) << " - " << dstr.substr(4) << '\n'; } // end if }// for(int d }// for(int mon }// for(int yr ... }

[Challenge] Palindromic_Dates.cpp