data-structures/cpp/dynamic_array_new.cpp

#include <iostream>
#include <sstream>
#include <algorithm>
#include <memory>

template<class T> class dynamic_array {
  private:
    std::shared_ptr<T> data {};
    size_t n {};

  public:
    dynamic_array(size_t n) {
      this -> n = n;
      data = std::make_shared<T[]>(n); 
    }

    dynamic_array(const dynamic_array<T>& other) {
      n = other.n;
      data = std::make_shared<T[]>(n);

      /* Here we perform a deep copy */
      for (size_t i {}; i < n; ++i) data[i] = other[i];
    }

    T& operator[](int index) {
      return data.get() + index;
    }

    const T& operator[](int index) const {
      return data[index];
    }

    T& at(size_t index) {
      if (index < n) return data[index];
      throw "Index out of range";
    }

    size_t size() const {
      return n;
    }

    ~dynamic_array() = default;

    std::shared_ptr<T> begin() {
      return data;
    }

    const std::shared_ptr<T> begin() const {
      return data;
    }

    std::shared_ptr<T> end() {
      return data + n;
    }

    const std::shared_ptr<T> end() const {
      return data + n;
    }

    friend dynamic_array<T> operator+(const dynamic_array<T>& arr1, dynamic_array<T>& arr2) {
      dynamic_array<T> result(arr1.size() + arr2.size());
      std::copy(arr1.begin(), arr1.end(), result.begin());
      std::copy(arr2.begin(), arr2.end(), result.begin() + arr1.size());

      return result;
    }

    std::string to_string(const std::string& sep = ", ") {
      if (n == 0) return "";
      std::ostringstream os {};
      os << data.get();

      for (size_t i {1}; i < n; ++i) os << sep << data.get() + i;

      return os.str();
    }
};

struct student {
  std::string name {};
  size_t standard {};
};

std::ostream& operator<<(std::ostream& os, const student& s) {
  return (os << "[Name: " << s.name << ", Standard: " << s.standard << "]");
}

int main() {
  size_t nStudents {};
  std::cout << "Enter number of students in class 1: ";
  std::cin >> nStudents;

  dynamic_array<student> class1(nStudents);
  for (size_t i {}; i < nStudents; ++i) {
    std::cout << "Enter name and class of student " << i + 1 << ": ";
    std::string name {};
    size_t standard {};
    std::cin >> name >> standard;
    class1[i] = student {name, standard};
  }

  // Now, let's tro to access the student out of range in the array
  try {
    class1[nStudents]  =student{"John", 8}; // No exception, endeffined behaviour
    std::cout << "class1 student set out of range without exception" << std::endl;
    class1.at(nStudents) = student{"John", 8}; // Will throw exception
  }
  catch(...) {
    std::cout << "Exception caught" << std::endl;
  }

  auto class2 = class1; // Deep copy
  
  std::cout << "Second class after initialized using first array: " << class2.to_string() << std::endl;

  auto class3 = class1 + class2; // Combines both classes and creates a bigger one

  std::cout << "Combined class: ";
  std::cout << class3.to_string() << std::endl;

  return 0;
}