CPP: make_shared and shared_ptr demo

main.cpp

#include <iostream>
#include <iomanip>
#include <vector>
#include <sstream>
#include <memory>
#include <cmath>

using namespace std;
const double PI = 3.14;

class Figure {
public:
 virtual string Name() const = 0;
 virtual double Perimeter() const = 0;
 virtual double Area() const = 0;
};

class Triangle : public Figure {
 public:
  Triangle(double a, double b, double c) : A(a), B(b), C(c) {}
  virtual string Name() const override { return "TRIANGLE"; }
  virtual double Perimeter() const override { return A + B + C; }
  virtual double Area() const override {
    double p = Perimeter() / 2;
    return sqrt(p * (p - A) * (p - B) * (p - C));
  }

 private:
  double A;
  double B;
  double C;
};
class Rect : public Figure {
 public:
  Rect(double w, double h) : W(w), H(h) {}
  virtual string Name() const override { return "RECT"; }
  virtual double Perimeter() const override { return (W + H) * 2; }
  virtual double Area() const override { return W * H; }

 private:
  double W;
  double H;
};
class Circle : public Figure {
 public:
  Circle(double r) : R(r) {}
  virtual string Name() const override { return "CIRCLE"; }
  virtual double Perimeter() const override { return 2*PI*R; }
  virtual double Area() const override { return PI*R*R; }

 private:
  double R;
};

shared_ptr<Figure> CreateFigure(istringstream& is) {
  string fig_name;
  is >> fig_name;
  if (fig_name == "RECT") {
    double w, h;
    is >> w >> h;
    return make_shared<Rect>(w, h);
  } else if (fig_name == "CIRCLE") {
    double r;
    is >> r;
    return make_shared<Circle>(r);
  } else if (fig_name == "TRIANGLE") {
    double a, b, c;
    is >> a >> b >> c;
    return make_shared<Triangle>(a, b, c);
  } else {
    throw logic_error("Incorrect figure type");
  }
}

int main() {
  vector<shared_ptr<Figure>> figures;
  for (string line; getline(cin, line); ) {
    istringstream is(line);

    string command;
    is >> command;
    if (command == "ADD") {
      figures.push_back(CreateFigure(is));
    } else if (command == "PRINT") {
      for (const auto& current_figure : figures) {
        cout << fixed << setprecision(3)
             << current_figure->Name() << " "
             << current_figure->Perimeter() << " "
             << current_figure->Area() << endl;
      }
    }
  }
  return 0;
}