Return the number of value_type objects within this unordered set that are equivalent to the specified key. Note that since an unordered set maintains unique keys, the returned value will be either 0 or 1.
value_type
key
Declared in <bslstl_unorderedset.h>
<bslstl_unorderedset.h>
size_type count(key_type const& key) const;