How can I use a C++ unordered_set for a custom class?

Question

How can I store objects of a class in an unordered_set? My program needs to frequently check if an object exists in this unordered_set and if it does,

Answer 1

Since this is the top Google result on Stack Overflow for C++ unordered_set of objects I'll post a simple yet completely illustrative and copy/paste runnable example:

// UnorderedSetOfObjects.cpp

#include 
#include 
#include 

struct Point
{
  int x;
  int y;

  Point() { }
  Point(int x, int y)
  {
    this->x = x;
    this->y = y;
  }
  
  bool operator==(const Point& otherPoint) const
  {
    if (this->x == otherPoint.x && this->y == otherPoint.y) return true;
    else return false;
  }

  struct HashFunction
  {
    size_t operator()(const Point& point) const
    {
      size_t xHash = std::hash()(point.x);
      size_t yHash = std::hash()(point.y) << 1;
      return xHash ^ yHash;
    }
  };
};

int main(void)
{
  std::unordered_set points;

  points.insert(Point(1, 1));
  points.insert(Point(2, 2));
  points.insert(Point(1, 1));   // notice this is a duplicate with the 1st point so it won't change the set

  std::cout << "points: " << "\n";
  for (auto& point : points)
  {
    std::cout << "(" << point.x << ", " << point.y << ")" << "\n";
  }

  return 0;
}