std::unordered_map::unordered_map
| (1) | ||
| explicit unordered_map( size_type bucket_count = /*implementation-defined*/, const Hash& hash = Hash(), |
(since C++11) (until C++14) |
|
| unordered_map() : unordered_map( size_type(/*implementation-defined*/) {} explicit unordered_map( size_type bucket_count, |
(since C++14) | |
| unordered_map( size_type bucket_count, const Allocator& alloc = Allocator() ); |
(1) | (since C++14) |
| explicit unordered_map( const Allocator& alloc ); |
(1) | (since C++11) |
| template< class InputIt > unordered_map( InputIt first, InputIt last, |
(2) | (since C++11) (since C++14) |
| unordered_map( const unordered_map& other ); |
(3) | (since C++11) |
| unordered_map( const unordered_map& other, const Allocator& alloc ); |
(3) | (since C++11) |
| unordered_map( unordered_map&& other ); |
(4) | (since C++11) |
| unordered_map( unordered_map&& other, const Allocator& alloc ); |
(4) | (since C++11) |
| unordered_map( std::initializer_list<value_type> init, size_type bucket_count = /*implementation-defined*/, |
(5) | (since C++11) (since C++14) |
Constructs new container from a variety of data sources. Optionally uses user supplied bucket_count as a minimal number of buckets to create, hash as the hash function, equal as the function to compare keys and alloc as the allocator.
max_load_factor() to 1.0. For the default constructor, the number of buckets is implementation-defined.[first, last). Sets max_load_factor() to 1.0.other, copies the load factor, the predicate, and the hash function as well. If alloc is not provided, allocator is obtained by calling std::allocator_traits<allocator_type>::select_on_copy_construction(other).other using move semantics. If alloc is not provided, allocator is obtained by move-construction from the allocator belonging to other.init, same as unordered_map(init.begin(), init.end()).Contents |
[edit] Parameters
| alloc | - | allocator to use for all memory allocations of this container |
| bucket_count | - | minimal number of buckets to use on initialization. If it is not specified, implementation-defined default value is used |
| hash | - | hash function to use |
| equal | - | comparison function to use for all key comparisons of this container |
| first, last | - | the range to copy the elements from |
| other | - | another container to be used as source to initialize the elements of the container with |
| init | - | initializer list to initialize the elements of the container with |
| Type requirements | ||
-InputIt must meet the requirements of InputIterator.
| ||
[edit] Complexity
first and lastotheralloc is given and alloc != other.get_allocator(), then linear.init[edit] Example
#include <unordered_map> #include <vector> #include <bitset> #include <string> #include <utility> struct Key { std::string first; std::string second; }; struct KeyHash { std::size_t operator()(const Key& k) const { return std::hash<std::string>()(k.first) ^ (std::hash<std::string>()(k.second) << 1); } }; struct KeyEqual { bool operator()(const Key& lhs, const Key& rhs) const { return lhs.first == rhs.first && lhs.second == rhs.second; } }; int main() { // default constructor: empty map std::unordered_map<std::string, std::string> m1; // list constructor std::unordered_map<int, std::string> m2 = { {1, "foo"}, {3, "bar"}, {2, "baz"}, }; // copy constructor std::unordered_map<int, std::string> m3 = m2; // move constructor std::unordered_map<int, std::string> m4 = std::move(m2); // range constructor std::vector<std::pair<std::bitset<8>, int>> v = { {0x12, 1}, {0x01,-1} }; std::unordered_map<std::bitset<8>, double> m5(v.begin(), v.end()); // constructor for a custom type std::unordered_map<Key, std::string, KeyHash, KeyEqual> m6 = { { {"John", "Doe"}, "example"}, { {"Mary", "Sue"}, "another"} }; }
[edit] See also
| assigns values to the container (public member function) |