| (1) | ||
explicit map( const Compare& comp = Compare(),
const Allocator& alloc = Allocator() ); | (until C++14) | |
map() : map( Compare() ) {}
explicit map( const Compare& comp,
const Allocator& alloc = Allocator() ); | (since C++14) | |
explicit map( const Allocator& alloc ); | (1) | (since C++11) |
| (2) | ||
template< class InputIterator >
map( InputIterator first, InputIterator last,
const Compare& comp = Compare(),
const Allocator& alloc = Allocator() ); | ||
template< class InputIterator >
map( InputIterator first, InputIterator last,
const Allocator& alloc ); | (since C++14) | |
map( const map& other ); | (3) | |
map( const map& other, const Allocator& alloc ); | (3) | (since C++11) |
map( map&& other ); | (4) | (since C++11) |
map( map&& other, const Allocator& alloc ); | (4) | (since C++11) |
| (5) | ||
map( std::initializer_list<value_type> init,
const Compare& comp = Compare(),
const Allocator& alloc = Allocator() ); | (since C++11) | |
map( std::initializer_list<value_type> init,
const Allocator& ); | (since C++14) |
Constructs new container from a variety of data sources and optionally using user supplied allocator alloc or comparison function object comp.
1) Default constructor. Constructs empty container.
2) Constructs the container with the contents of the range
[first, last). 3) Copy constructor. Constructs the container with the copy of the contents of
other. If alloc is not provided, allocator is obtained by calling std::allocator_traits<allocator_type>::select_on_container_copy_construction(other.get_allocator()). 4) Move constructor. Constructs the container with the contents of
other using move semantics. If alloc is not provided, allocator is obtained by move-construction from the allocator belonging to other. 5) Constructs the container with the contents of the initializer list
init. Parameters
| alloc | - | allocator to use for all memory allocations of this container |
| comp | - | comparison function object to use for all comparisons of keys |
| 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 | ||
- InputIterator must meet the requirements of InputIterator. | ||
- Compare must meet the requirements of Compare. | ||
- Allocator must meet the requirements of Allocator. | ||
Complexity
1) Constant
2) N log(N) where
N = std::distance(first, last) in general, linear in N if the range is already sorted by value_comp(). 3) Linear in size of
other 4) Constant. If
alloc is given and alloc != other.get_allocator(), then linear. 5) N log(N) where
N = init.size()) in general, linear in N if init is already sorted by value_comp().Example
#include <iostream>
#include <string>
#include <iomanip>
#include <map>
template<typename Map>
void print_map(Map& m)
{
std::cout << '{';
for(auto& p: m)
std::cout << p.first << ':' << p.second << ' ';
std::cout << "}\n";
}
int main()
{
// (1) Default constructor
std::map<std::string, int> map1;
map1["something"] = 69;
map1["anything"] = 199;
map1["that thing"] = 50;
std::cout << "map1 = "; print_map(map1);
// (2) Range constructor
std::map<std::string, int> iter(map1.find("anything"), map1.end());
std::cout << "\niter = "; print_map(iter);
std::cout << "map1 = "; print_map(map1);
// (3) Copy constructor
std::map<std::string, int> copied(map1);
std::cout << "\ncopied = "; print_map(copied);
std::cout << "map1 = "; print_map(map1);
// (4) Move constructor
std::map<std::string, int> moved(std::move(map1));
std::cout << "\nmoved = "; print_map(moved);
std::cout << "map1 = "; print_map(map1);
// (5) Initializer list constructor
const std::map<std::string, int> init {
{"this", 100},
{"can", 100},
{"be", 100},
{"const", 100},
};
std::cout << "\ninit = "; print_map(init);
}Output:
map1 = {anything:199 something:69 that thing:50 }
iter = {anything:199 something:69 that thing:50 }
map1 = {anything:199 something:69 that thing:50 }
copied = {anything:199 something:69 that thing:50 }
map1 = {anything:199 something:69 that thing:50 }
moved = {anything:199 something:69 that thing:50 }
map1 = {}
init = {be:100 can:100 const:100 this:100 }See also
| operator=
| assigns values to the container (public member function) |
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