24 Containers library [containers]

24.5 Unordered associative containers [unord]

24.5.6 Class template unordered_set [unord.set]

24.5.6.2 Constructors [unord.set.cnstr]

unordered_set() : unordered_set(size_type(see below)) { } explicit unordered_set(size_type n, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());
Effects: Constructs an empty unordered_set using the specified hash function, key equality predicate, and allocator, and using at least n buckets.
For the default constructor, the number of buckets is implementation-defined.
max_load_factor() returns 1.0.
Complexity: Constant.
template<class InputIterator> unordered_set(InputIterator f, InputIterator l, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); template<container-compatible-range<value_type> R> unordered_multiset(from_range_t, R&& rg, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); unordered_set(initializer_list<value_type> il, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());
Effects: Constructs an empty unordered_set using the specified hash function, key equality predicate, and allocator, and using at least n buckets.
If n is not provided, the number of buckets is implementation-defined.
Then inserts elements from the range [f, l), rg, or il, respectively.
max_load_factor() returns 1.0.
Complexity: Average case linear, worst case quadratic.