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C++ Map Library - map() Function
Description
The C++ constructor std::map::map() constructs a map with as many elements as in range of first to last.
Declaration
Following is the declaration for std::map::map() constructor form std::map header.
C++98
template <class InputIterator> map (InputIterator first, InputIterator last, const key_compare& comp = key_compare(), const allocator_type& alloc = allocator_type());
C++11
template <class InputIterator> map (InputIterator first, InputIterator last, const key_compare& comp = key_compare(), const allocator_type& = allocator_type());
Parameters
first − Input iterator to initial position.
last − Input iterator to final position.
comp − A binary predicate, which takes two key arguments and returns true if first argument goes before second otherwise false. By default it uses less<key_type> predicate.
alloc − The allocator object.
Return value
Constructor never returns value.
Exceptions
This member function never throws exception.
Time complexity
Linear i.e. O(n)
Example
The following example shows the usage of std::map::map() constructor.
#include <iostream> #include <map> using namespace std; int main(void) { map<char, int> m1 = { {'a', 1}, {'b', 2}, {'c', 3}, {'d', 4}, {'e', 5} }; map<char, int> m2(m1.begin(), m1.end()); cout << "Map contains following elements" << endl; for (auto it = m2.begin(); it != m2.end(); ++it) cout << it->first << " = " << it->second << endl; return 0; }
Let us compile and run the above program, this will produce the following result −
Map contains following elements a = 1 b = 2 c = 3 d = 4 e = 5
map.htm
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