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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
 
// 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;
}


Output:
a => 200
b => 100
c => 300


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)