unordered_map::unordered_map
Constructs a container object.
unordered_map(
const unordered_map& right);
explicit unordered_map(
size_type nbuckets = N0,
const Hash& hfn = Hash(),
const Pred& comp = Pred(),
const Alloc& al = Alloc());
template<class InIt>
unordered_map(
InIt first, InIt last,
size_type nbuckets = N0,
const Hash& hfn = Hash(),
const Pred& comp = Pred(),
const Alloc& al = Alloc());
unordered_map(
unordered_map&& right);
Parameters
Parameter |
Description |
InIt |
The iterator type. |
al |
The allocator object to store. |
comp |
The comparison function object to store. |
hfn |
The hash function object to store. |
nbuckets |
The minimum number of buckets. |
right |
The container to copy. |
Remarks
The first constructor specifies a copy of the sequence controlled by right. The second constructor specifies an empty controlled sequence. The third constructor inserts the sequence of element values [first, last). The fourth constructor specifies a copy of the sequence by moving right.
All constructors also initialize several stored values. For the copy constructor, the values are obtained from right. Otherwise:
the minimum number of buckets is the argument nbuckets, if present; otherwise it is a default value described here as the implementation-defined value N0.
the hash function object is the argument hfn, if present; otherwise it is Hash().
the comparison function object is the argument comp, if present; otherwise it is Pred().
the allocator object is the argument al, if present; otherwise, it is Alloc().
Example
// std_tr1__unordered_map__unordered_map_construct.cpp
// compile with: /EHsc
#include <unordered_map>
#include <iostream>
typedef std::unordered_map<char, int> Mymap;
int main()
{
Mymap c1;
c1.insert(Mymap::value_type('a', 1));
c1.insert(Mymap::value_type('b', 2));
c1.insert(Mymap::value_type('c', 3));
// display contents " [c 3] [b 2] [a 1]"
for (Mymap::const_iterator it = c1.begin();
it != c1.end(); ++it)
std::cout << " [" << it->first << ", " << it->second << "]";
std::cout << std::endl;
Mymap c2(8,
std::tr1::hash<char>(),
std::equal_to<char>(),
std::allocator<std::pair<const char, int> >());
c2.insert(Mymap::value_type('d', 4));
c2.insert(Mymap::value_type('e', 5));
c2.insert(Mymap::value_type('f', 6));
// display contents " [f 6] [e 5] [d 4]"
for (Mymap::const_iterator it = c2.begin();
it != c2.end(); ++it)
std::cout << " [" << it->first << ", " << it->second << "]";
std::cout << std::endl;
Mymap c3(c1.begin(),
c1.end(),
8,
std::tr1::hash<char>(),
std::equal_to<char>(),
std::allocator<std::pair<const char, int> >());
// display contents " [c 3] [b 2] [a 1]"
for (Mymap::const_iterator it = c3.begin();
it != c3.end(); ++it)
std::cout << " [" << it->first << ", " << it->second << "]";
std::cout << std::endl;
Mymap c4(std::move(c3));
// display contents " [c 3] [b 2] [a 1]"
for (Mymap::const_iterator it = c4.begin();
it != c4.end(); ++it)
std::cout << " [" << it->first << ", " << it->second << "]";
std::cout << std::endl;
return (0);
}
[c, 3] [b, 2] [a, 1] [f, 6] [e, 5] [d, 4] [c, 3] [b, 2] [a, 1] [c, 3] [b, 2] [a, 1]
Requirements
Header: <unordered_map>
Namespace: std