main.cpp

#include <iostream>

#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <algorithm>

#ifndef in
#define in std::cin
#endif // in
#ifndef out
#define out std::cout
#endif // out
#ifndef nl
#define nl std::endl
#endif // nl

using std::string;
using std::back_inserter;
using std::count_if;
using std::transform;
using std::to_string;
using std::vector;
using std::pair;
using std::map;
using std::unordered_multimap;

template<typename K, typename V>
string to_string(const map<K, V> map) {
    string value = "{";
    {
        const auto end = map.end();
        auto not_first = false;
        for (auto iterator = map.begin(); iterator != end; iterator++) {
            if (not_first) value += ", ";
            else not_first = true;

            const auto pair = *iterator;
            value += (to_string(pair.first) + ":" + pair.second);
        }
    }
    return value + "}";
}

template<typename K, typename V>
string to_string(const unordered_multimap<K, V> map) {
    string value = "{";
    {
        const auto end = map.end();
        auto not_first = false;
        for (auto iterator = map.begin(); iterator != end; iterator++) {
            if (not_first) value += ", ";
            else not_first = true;

            const auto pair = *iterator;
            value += (to_string(pair.first) + ":" + pair.second);
        }
    }
    return value + "}";
}

int main() {
    unordered_multimap<int, string> original_map;

    /* Task 1 */
    {
        size_t size;
        out << "Insert size: ";
        in >> size;
        for (size_t i = 0; i < size; i++) {
            out << "Insert key and value: ";
            int key;
            string value;
            in >> key >> value;
            original_map.insert(pair<int, string>(key, value));
        }
        out << "Read collection: " << to_string(original_map) << nl;
    }
    {
        original_map.erase(5);
        original_map.erase(8);
        out << "After erasing: " << to_string(original_map) << nl;
    }
    {
        for (auto i = 0U; i < 2U; i++) {
            out << "Insert value for key 2: ";
            string value;
            in >> value;
            original_map.insert(pair<int, string>(2, value));
        }
        out << "After adding two values at 2: " << to_string(original_map) << nl;
    }
    map<int, string> shortened_map;
    {
        const auto end = original_map.end();
        for (auto iterator = original_map.begin(); iterator != end; iterator++) {
            const auto pair = *iterator;
            shortened_map.insert(::pair<int, string> (pair.first, pair.second));
        }
        out << "Shortened map: " << to_string(shortened_map) << nl;
    }

    /* Task 2 */
    {
        out << "Number of positive elements: " << count_if(
                shortened_map.begin(), shortened_map.end(),
                [](const pair<int, string> &pair) { return pair.first > 0; }
        );
    }
    vector<int> keys;
    transform(
            shortened_map.begin(), shortened_map.end(), std::back_inserter(keys),
            [](const pair<const int, const string>& pair) { return pair.first; }
    );



    return 0;
}