#include <functional>
#include <future>
#include <execution>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>

using namespace std;

vector<string_view> Split(string_view str) {
    vector<string_view> result;
    while (true) {
        const auto space = str.find(' ');
        if (space != 0 && !str.empty()) {
            result.push_back(str.substr(0, space));
        }
        if (space == str.npos) {
            break;
        } else {
            str.remove_prefix(space + 1);
        }
    }
    return result;
}

struct Stats {
    map<string, int> word_frequences;

    void operator+=(const Stats &other) {
        for (const auto &it: other.word_frequences) {
            word_frequences[it.first] += it.second;
        }
    }
};

using KeyWords = set<string, less<>>;

Stats foo(const KeyWords &key_words, vector<string> dataset) {
    Stats stat;
    std::for_each(execution::par,
                  dataset.begin(), dataset.end(),
                  [&key_words, &stat](const auto line) {
                      for (const auto word: Split(line)) {
                          if (key_words.count(word) > 0) {
                              ++stat.word_frequences[string(word)];
                          }
                      }
                  });
    return stat;
}

Stats ExploreKeyWords(const KeyWords &key_words, istream &input) {
    const size_t MAX_SIZE = 5000;
    vector<string> dataset;
    dataset.reserve(MAX_SIZE);
    vector<future<Stats>> futures;
    for (string line; getline(input, line);) {
        dataset.push_back(std::move(line));
        if (dataset.size() >= MAX_SIZE) {
            futures.push_back(async(foo, cref(key_words), dataset));
            dataset.clear();
        }
    }
    Stats result;
    if (!dataset.empty()) {
        result += foo(cref(key_words), dataset);
    }
    std::for_each(std::execution::par,
                  futures.begin(), futures.end(),
                  [&result](auto &f) { result += f.get(); });
    return result;
}

int main() {
    const KeyWords key_words = {"yangle", "rocks", "sucks", "all"};

    stringstream ss;
    ss << "this new yangle service really rocks\n";
    ss << "It sucks when yangle isn't available\n";
    ss << "10 reasons why yangle is the best IT company\n";
    ss << "yangle rocks others suck\n";
    ss << "Goondex really sucks, but yangle rocks. Use yangle\n";

    for (const auto &[word, frequency]: ExploreKeyWords(key_words, ss).word_frequences) {
        cout << word << " " << frequency << endl;
    }

    return 0;
}