Generic topological sorting for sorting a list of dependencies in C++17

Use

There are two interfaces to choose from: dep_sort_stl and dep_sort.

The first will use std::vector, std::unordered_set and std::unordered_map to implement a highly efficent O(V+E) dependency resolver container.

There's also however a dep_sort class which lets you supplement your own vector, set and map implementions. You can use drop in replacements like Google's densehash or sparsehash and stuff like Boost's multimap if working with highly dense or sparse data.

As a result this code has no real dependencies other than a working C++17 compiler.

Example

int main() {
  dep_sort_stl<std::string> dep;
  dep.add_node("a");
  dep.add_node("b");
  dep.add_node("c");
  dep.add_node("d");
  std::vector<std::string> as = { "b", "c" };
  std::vector<std::string> bs = { "c" };
  std::vector<std::string> cs = { "d" };
  dep.add_dependencies("a", as);
  dep.add_dependencies("b", bs);
  dep.add_dependencies("c", cs);
  const auto& result = dep.sort();
  if (!result.has_cycles()) {
    // print the sorted list
    for (const auto& value : result.sorted) {
      std::cout << value << std::endl;
    }
  } else {
    // print nodes that could not be sorted due to cycles
    for (const auto& value : result.unsorted) {
      std::cout << value << std::endl;
    }
  }
}

Documentation

The interfaces are documented in dep_sort.h