seminar 2023-01-20

// sem 2
//Hello world

// vector<int> v = {1, 2, 3};
// cout << v << "\n";

struct string {
    size_t capacity;

    union {
        struct {
            size_t size;
            char* data;
        } long_data;

        char[16] short_data;
    } data;
};

struct SelfCounting {
    SelfCounting() {
        data = 0;
        cout << "SelfCounting()\n";
    }

    SelfCounting(int d) {
        cout << "SelfCounting(int)\n";
        data = d;
    }

    SelfCounting(const SelfCounting& rhs) {
        cout << "SelfCounting(copy)\n";
        data = rhs.data;
    }

    int data;
};

ostream& operator<< (ostream& str, const SelfCounting& sc) {
    return str << sc.data;
}

SelfCounting by_val(SelfCounting obj) {
    cout << obj << "\n";
    return obj;
}

SelfCounting by_ref(const SelfCounting& obj) {
    cout << obj << "\n";
    return obj;
}

// itoa(45) -> string "45"
// itoa(12345) -> "12345"
// itoa(-443) -> "-443"
// '0' + 5 == '5'
string itoa(int value) {
    std::string result = "";
    result.reserve(15);
    bool minus_flag = false;
    if (value < 0) {
        minus_flag = true;
        value *= -1;
    }
    while (value > 0) {
        result += '0' + value % 10;
        value /= 10;
    }
    // return {result.rbegin(), result.rend()}
    if (minus_flag) {
        result += "-";
    }
    std::reverse(result.begin(), result.end());
    result.shrink_to_fit();
    return result;
}

template <typename T>
ostream& operator<< (ostream& os, const vector<T>& v) {
    // [1, 2, 3]
    os << "[";
    for (std::size_t i = 0; i < v.size() - 1; ++i) {
        os << v[i] << ", ";
    }
    if (!v.empty()) {
        os << v[v.size() - 1];
    }
    return os << "]";
}

void dangling() {
    int c_v[3] = {1,2,3}

    vector<int> v = {1, 2, 3};
    v.reserve(4);

    int& f = v[0];
    f = 4;
    cout << v;  // 4, 2, 3

    v.push_back(5);
    cout << f;  //<

    int* p = &v[0];
    cout << *p;

    for (i = v.begin(); i != v.end(); ) {
        if (*i == 42)
            i = v.erase(i);
        else
            i++;
    }
}


void matrix_ops() {
    vector<vector<int>> matrix = {
        {1, 2, 3},
        {4, 5, 6},
    };

    cout << matrix << "\n";
    for (const auto& row : matrix) {
        for (int e : row)
            cout << e << " ";
        cout << "\n";
    }

    for (size_t i = 0; i < matrix.size(); ++i) {
        for (size_t j = 0; j < matrix[i].size(); ++j)
            cout << matrix[i][j] << " ";
        cout << "\n";
    }
}

void charmap() {
    for (int i = 0; i < 256; i++)
        cout << i << ": " << static_cast<char>(i) << "\n";

    char c;
    'A' <= c && c <= 'Z';
}

void charmap_pretty() {
    using std::hex, std::cout;
    const size_t cols = 16;
    cout << "  |";
    for (size_t  c = 0; c < cols; c++)
        cout << hex << c << " ";
    cout << "\n--+-";
    for (size_t c = 0; c < cols; c++)
        cout << "--";

    for (unsigned char c = 0; c < 255; c++) {
        if ((c & 0xF) == 0) {
            cout << "\n" << hex << (c >> 4) << " | ";
        }
        cout << c << " ";
    }
    cout << "\n";
}

struct Date {
    int year;
    int month;
    uint8_t day;
};

void print_date(const Date& d) {
    cout << d.year << "-" << d.month << "-" << d.day << "\n";
}

string& concat(const string& l, const string& r) {
    string result = l;
    result += r;
    return result;
}

void structs() {
    Date ub;
    print_date(ub);
    print_date({2023});
    print_date({2023, 1});
    print_date({2023, 1, 20});
    print_date({.month = 1});
    print_date({.month = 1, .day = 20});
}

bool is_even(int i) {
    return i % 2 == 0;
}

bool date_year_less(const Date& l, const Date& r) {
    return l.year < r.year;
}

void evens(const vector<int>& data) {
    size_t count = std::count_if(data.begin(), data.end(), is_even);

    cout << count << "\n";
}

int do_pref_sum(int i) {
    static int p = 0;
    p += i;
    return p;
}

void prefix_sum(const vector<int> v) {
    vector<int> prefs;
    prefs.resize(v.size());
    std::transform(v.rbegin(), v.rend(), prefs.rbegin(), do_pref_sum);

    cout << v << "\n" << prefs << "\n";
}

int main(int, const char**) {
    prefix_sum({1, 2, 3});

    return 0;

    vector<Date> dates = {
        {2023, 1, 1},
        {2022, 1, 10},
    };

    cout << dates << "\n";
    std::sort(dates.begin(), dates.end(), date_year_less);
    cout << dates << "\n";

    return 0;
}


// vector<vector<int>> m;
// cout << m << "\n";
// [[1,2,3],[4,5,6]]