c++ overloading

#include <iostream>
#include <vector>
#include <string>

void swap(int &a, int &b)
{
  int temp = a;
  a = b;
  b = temp;
  std::cout << "a: " << a << "\tb: " << b << "\n";
}

void swap(std::string &a, std::string &b)
{
  std::string temp = a;
  a = b;
  b = temp;
}

int main()
{
  int a = 10;
  int b = 20;
  swap(a, b);
  std::string c = "Jim";
  std::string d = "Lucy";
  swap(c, d);
  std::cout << "In main: \n";
  std::cout << "a: " << a << "\tb: " << b << "\n";
  std::cout << "c: " << c << "\td: " << d << "\n";
  return 0;
}

#include <iostream>
#include <vector>
#include <string>

struct Rectangle
{
  double length;
  double width;
};

double area(double length, double width)
{
  return length * width;
}

double area(double length)
{
  return length * length;
}

double area(Rectangle rectangle)
{
  return rectangle.length * rectangle.width;
}

int main()
{
  Rectangle rectangle;
  rectangle.length = 10;
  rectangle.width = 10;
  std::cout << area(rectangle.length, rectangle.width) << std::endl;
  std::cout << area(rectangle.length) << std::endl;
  std::cout << area(rectangle) << std::endl;
  return 0;
}