22 Containers library [containers]

22.5 Unordered associative containers [unord]

22.5.6 Class template unordered_­set [unord.set]

22.5.6.2 Constructors [unord.set.cnstr]

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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());
1
#
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.
2
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Complexity: Constant.
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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()); 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());
3
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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) for the first form, or from the range [il.begin(), il.end()) for the second form.
max_­load_­factor() returns 1.0.
4
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Complexity: Average case linear, worst case quadratic.