map::begin
public member function
iterator begin ();
const_iterator begin () const;
Return iterator to beginning
Returns an iterator referring to the first element in the map container.
Internally, map containers keep their elements ordered by their keys from lower to higher , therefore begin returns the element with the lowest key value in the map.
Parameters
none
Return Value
An iterator to the first element in the container.
Both iterator and const_iterator are member types. In the map class template, these are bidirectional iterators.
Dereferencing this iterator accesses the element's value, which is of type pair<const Key,T>.
Example
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// map::begin/end
#include <iostream>
#include <map>
using namespace std;
int main ()
{
map<char,int> mymap;
map<char,int>::iterator it;
mymap['b'] = 100;
mymap['a'] = 200;
mymap['c'] = 300;
// show content:
for ( it=mymap.begin() ; it != mymap.end(); it++ )
cout << (*it).first << " => " << (*it).second << endl;
return 0;
}
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Output:
a => 200
b => 100
c => 300
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Complexity
Constant.
See also
| map::end | Return iterator to end (public member function) |
| map::rbegin | Return reverse iterator to reverse beginning (public member function) |
| map::rend | Return reverse iterator to reverse end (public member function) |
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