c++ custom compare in set

To create a custom comparison function for a set in C++, you can define a struct or class to overload the function call operator. This custom comparison function should return true if the first argument is considered less than the second argument, and false otherwise. The set should be declared with the custom comparison function type as the third template parameter. When inserting elements into the set, the custom comparison function will be used to maintain the set's order according to the defined criteria.