A C++ implementation of a fast hash map and hash set using hopscotch hashing

The hopscotch-map library is a C++ header-only implementation of hash maps and sets using hopscotch hashing that generally outperforms std::unordered_map with better cache efficiency and lower memory usage. It offers multiple variants including standard and prime growth policy versions, as well as balanced versions that provide O(log n) worst-case performance for DoS attack resistance. The library features fast lookups, support for move-only types, heterogeneous lookups, and an API similar to std::unordered_map with some differences in iterator invalidation behavior.