I was refreshing some algorithm knowledge and implementing djikstra in c++ and saw this seemingly broken behavior in std::priority_queue. Can anyone shed some light on why I might be seeing this? I created a priority_queue with a custom comparator, to allow me to insert indices into the priority_queue and prioritize them based on the minimum… Read More Why is my std::priority_queue with custom comparator ordering elements incorrectly?

I was reading through the MSVC STL implementation of std::ranges::remove when I noticed the following line: _First = _RANGES _Find_if_unchecked(_STD move(_First), _Last, _Pred, _Proj); Indeed, cppreference has the following line in their ‘possible implementation’ too: first = ranges::find_if(std::move(first), last, pred, proj); What’s confusing to me is, I’ve just about never seen anyone move an iterator;… Read More Why do the new ranges remove_* algorithms *move* the `first` pointer?

What is the recommended way to store a reference to a non-static member function of a specific signature on some object instance? In a way where the calling code needs not to know of the object’s class (i.e. no casting), just that the function is the correct signature. For example, if there are two different… Read More How to store a specific object's member function of known signature in a variable in C++?

Recently I learnt about comparators in cpp from STL. I came to know we can use greater<>() as third argument for sorting instead of writing own logic. Just curious to know how many inbuilt comparators are there in cpp. >Solution : The standard library defines pretty much what you would expect as analogues to the… Read More Inbuilt / pre-defined comparator in cpp

These are two pieces of code that I ran under the C++11 standard. I expected the post-decrement of the iterator to produce the same effect, but these two pieces of code produce completely different results. Where is my understanding off? list<int> L; int main() { L.push_back(0); L.push_front(1); auto it = L.begin(); for (int i =… Read More Why does "L.insert(it–, i);" behave differently from "L.insert(it, i); it–;"?

I came across a paragraph on cppreference that I don’t think I understand: No iterators or references are invalidated. [If the insertion is successful, pointers and references to the element obtained while it is held in the node handle are invalidated, and pointers and references obtained to that element before it was extracted become valid.… Read More std::set elements' reference and pointer invariance after insertion

To me, it looks like an implementation of std::shared_ptr which stores a reference counter in a static std::unordered_map<void*, struct Counters> would be much more simpler and also allow us to avoid some dirty workarounds like std::enable_shared_from_this (because std::shared_ptr<T>{this} wouldn’t create new control block, only increment a counter for a pointer that already exists in a… Read More Why is shared_ptr implemented using control block and not a static map?

I’m a beginner at templates in C++ and I would like to know if it’s possible to pass a container to the typename of a template function, here is what I’m trying to do: template <typename T> int find_size(const T<int> t) { return (t.size()); } int main(void) { std::array<int, 10> test; for (int i =… Read More Pass a container type as the typename of a template in c++