samp

#include <iostream>
#include <tuple>
#include <map>
#include<functional>
#include <set>
#include <vector>

class Date
{
private:

    std::tuple<int,int,int> dateTuple;

public:

    Date(const int &day, const int &month, const int &year)
    {
        this->dateTuple=std::make_tuple(day, month, year);
    }

    std::tuple<int,int,int> getTuple()
    {
        return this->dateTuple;
    }

    bool isLess(Date *date)
    {

        if(std::get<2>(this->dateTuple)<std::get<2>(date->getTuple())) //compare year
            return true;

        if(std::get<1>(this->dateTuple)<std::get<1>(date->getTuple())) //compare month
            return true;

        if(std::get<0>(this->dateTuple)<std::get<0>(date->getTuple()))  //compare day
            return true;

        return false;
    }
};

class   Calendar
{
private:

    std::map<Date*, std::vector<std::string>> calendar;

//    std::vector<std::map<Date*, std::string>> calendar;

public:

    void mapEvent(const std::string &eventName, Date* date)
    {

        std::vector<std::string> v;
        v.push_back(eventName);
        //calendar[date]=v;

        calendar.insert(std::pair<Date*, std::vector<std::string>>(date, v));
    }

    std::string getEvent(Date *date)
    {
        std::string str="";

        for(auto& cal : calendar)
        {
            if(cal.first==date)
            {
                for(auto& evName : cal.second)
                {
                    str.append(evName);
                }
            }
        }
        return str;
    }


void printSortedEvents()
{
    // Declaring the type of Predicate that accepts 2 pairs and return a bool
    typedef std::function<bool(std::pair<Date*, std::string>, std::pair<Date*, std::string>)> Comparator;

    // Defining a lambda function to compare two pairs. It will compare two pairs using second field
    Comparator compFunctor =
        [](std::pair<Date*, std::string> elem1,std::pair<Date*, std::string> elem2)
    {
        return elem1.first->isLess(elem2.first);
    };

    // Declaring a set that will store the pairs using above comparision logic
    std::set<std::pair<Date*, std::string>, Comparator> dates(
        calendar.begin(), calendar.end(), compFunctor);

    // Iterate over a set using range base for loop
    // It will display the items in sorted order of values
    for (std::pair<Date*, std::string> element : dates)
        std::cout << element.second << std::endl;
}
};

int main()
{
    Date d(24, 5, 2019);
    Date d1(25, 5, 2019);
    Date d2(25, 5, 2020);
    Date d3(25, 5, 2019);
    Date d4(26, 5, 2019);

    Calendar calendar;

    calendar.mapEvent("first event", &d);
    calendar.mapEvent("last event", &d2);
    calendar.mapEvent("not first event", &d1);
    calendar.mapEvent("not first event2", &d1);

    calendar.printSortedEvents();

    return 0;
}