Use auto (which in the end will be ptrdiff_t) instead of size_t for the distance between the two iterators on the range insert. This way we avoid any problem if 'first' iterator come after 'last'.
Use auto (which in the end will be ptrdiff_t) instead of size_t for the distance between the two iterators on the range insert. This way we avoid any problem if 'first' iterator come after 'last'.

Tessil/hopscotch-map