#include <iostream>
#include <algorithm> //For std::swap
#include <memory> //For std::unique_ptr
#include <vector>
 
//std::make_unique implementation (it was forgotten in the C++11 standard, and will be added later).
//Once it's added, I can just remove this from here.
template<typename T, typename ...Args>
std::unique_ptr<T> make_unique( Args&& ...args )
{
	return std::unique_ptr<T>( new T( std::forward<Args>(args)... ) );
}
 
//Swaps and pops every element in 'container', for which the callback function 'predicate(element)' returns false.
//This is faster than std::remove_if(), but does not preserve the order of the elements like 'remove_if()' does.
template<typename ContainerType, typename FunctionType>
void SwapAndPop(ContainerType &container, FunctionType predicate)
{
	for(typename ContainerType::iterator it = container.begin(); it != container.end();)
	{
		if(predicate(*it))
		{
			//Swap the value of the current element with the element at the back of the container.
			std::swap(*it, container.back());
			//Pop the back of the container.
			container.pop_back();
 
			if(container.empty())
			{
				break;
			}
		}
		else
		{
			++it;
		}
	}
}
 
class Object
{
	static unsigned nextID;
 
	public:
	Object() : timeToDelete(++nextID % 3), id(nextID) { }
 
	bool timeToDelete = false;
	size_t id = 0;
 
	public:
	typedef std::unique_ptr<Object> uPtr;
};
 
unsigned Object::nextID = 0;
 
int main()
{
	const size_t NumObjectsForTest = 40;
 
	std::vector<Object::uPtr> objects;
 
	//Create all the objects.
	for(size_t i = 0; i < NumObjectsForTest; ++i)
	{
		objects.push_back(make_unique<Object>());
	}
 
	//Print all the objects.
	for(const auto &object : objects)
	{
		std::cout << "Object " << object->id << ": " << (object->timeToDelete? "[Time to delete]":"[Still alive]") << std::endl;
	}
 
	std::cout << "------------------------------------\n"
	          << "Calling SwapAndPop...\n"
	          << "------------------------------------\n";
 
	SwapAndPop(objects, [](Object::uPtr &objectPtr) -> bool { return objectPtr->timeToDelete; });
 
	//Print all the objects again.
	for(const auto &object : objects)
	{
		std::cout << "Object " << object->id << ": " << (object->timeToDelete? "[Time to delete]":"[Still alive]") << std::endl;
	}
 
	return 0;
}

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