#include <iostream>
#include <vector>


using namespace std;

class Vector {

public:
    Vector() {
        arr_ = new int[4];
        size_ = 0;
        capacity_ = 4;
    }

    Vector(const int capacity) {
        arr_ = new int[capacity];
        size_ = 0;
        capacity_ = capacity;
    }

    void push_back(const int value) {
        if (size_ == capacity_) {
            int* temp = new int[capacity_ * 2];
            for (int i = 0; i < size_; i++) {
                temp[i] = arr_[i];
            }
            delete[] arr_;
            arr_ = temp;
            capacity_ *= 2;
        }
        arr_[size_] = value;
        size_++;
    }

    void insert(const int index, const int value) {

    }

    void pop_back() {
        if (size_ > 0) {
            size_--;
        }
    }

    void print() {
        for (int i = 0; i < size_; i++) {
            cout << arr_[i] << " ";
        }
        cout << endl;
    }

private:
    int* arr_; // хранилище
    int size_; // текущее количество элементов
    int capacity_; // емкость хранилища
};

int main() {
    setlocale(LC_ALL, "ru");

    Vector vec1;

    vec1.push_back(10);
    vec1.push_back(15);
    vec1.push_back(20);
    vec1.push_back(25);

    vec1.print();

    vec1.pop_back();
    vec1.print();
}