C++ 内置函数的拓展应用和自定义案例

struct Person {
    string name;
    int age;
};

bool comparePerson(const Person& a, const Person& b) {
    return a.age > b.age;
}

vector<Person> people = {{"Alice", 25}, {"Bob", 30}, {"Carol", 22}};

sort(people.begin(), people.end(), comparePerson);

struct Book {
    string title;
    double price;
};

bool compareBook(const Book& a, const Book& b) {
    return a.price < b.price;
}

const Book book1 = {"The Hobbit", 10.99};
const Book book2 = {"The Lord of the Rings", 15.99};

cout << "Cheapest book: " << min(book1, book2, compareBook).title << endl;

class VectorIterator {
private:
    vector<int>& vector;
    int position;

public:
    VectorIterator(vector<int>& vector) : vector(vector), position(0) {}

    int operator*() const { return vector[position]; }
    VectorIterator& operator++() { ++position; return *this; }
    bool operator==(const VectorIterator& other) const { return position == other.position; }
    bool operator!=(const VectorIterator& other) const { return !(*this == other); }
};

vector<int> vec = {1, 2, 3, 4, 5};
for (VectorIterator it = VectorIterator(vec); it != VectorIterator(); ++it) {
    cout << *it << " ";
}

struct Summator {
    int operator()(int a, int b) const { return a + b; }
};

int sum(vector<int>& numbers, const Summator& functor) {
    int total = 0;
    for (int num : numbers) {
        total = functor(total, num);
    }
    return total;
}

vector<int> numbers = {1, 2, 3, 4, 5};
cout << "Sum of numbers: " << sum(numbers, Summator()) << endl;