Given two absolute paths A and B, how to get the relative path from A to B

I have a programm which generates a header and a source file, both can be stored in different directionaries from each other. I want to have the header file as an include in the source file, here is my problem how can I construct the include such that it's working even if they are in completly different dirs?

E.g. source path: C:/AA/BB/EE/source.cpp , header path: C:/AA/CC/DD/header.h => #include "../../CC/DD/header.h (No absolut paths in the include, no use of third party libraries).

My current idea is that I split both paths between the slashes, put them into an array and compare them, but I can't figure out the rest.

You can use std::filesystem::relative:

#include <iostream>
#include <filesystem>

int main() {
    auto p = std::filesystem::relative("a/b/c/d","a/b/x/y");
    std::cout << p;
}

Output:

"../../c/d"