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==const_iterator for map==

<source lang="cpp">#include <map>
#include <iostream>
using namespace std;
typedef map <int, string> MAP_INT_STRING;
typedef multimap <int, string> MMAP_INT_STRING;
int main ()
{
MAP_INT_STRING mapIntToString;
mapIntToString.insert (MAP_INT_STRING::value_type (3, "Three"));
MAP_INT_STRING::const_iterator iMapPairLocator;
for ( iMapPairLocator = mapIntToString.begin (); iMapPairLocator != mapIntToString.end (); ++ iMapPairLocator )
{
cout << "Key: " << iMapPairLocator->first;
cout << " Value: " << iMapPairLocator->second.c_str ();
cout << endl;
}
return 0;
}</source>

==Create int string map and print all element pair==

<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
// type of the collection
typedef multimap<int,string> IntStringMMap;
IntStringMMap coll; // container for int/string values
// insert some elements in arbitrary order
// - a value with key 1 gets inserted twice
coll.insert(make_pair(5,"tagged"));
coll.insert(make_pair(2,"a"));
coll.insert(make_pair(1,"this"));
coll.insert(make_pair(4,"of"));
coll.insert(make_pair(6,"strings"));
coll.insert(make_pair(1,"is"));
coll.insert(make_pair(3,"multimap"));
/* print all element values
* - iterate over all elements
* - element member second is the value
*/
IntStringMMap::iterator pos;
for (pos = coll.begin(); pos != coll.end(); ++pos) {
cout << pos->second << " ";
}
cout << endl;
}</source>
<pre class=codeResult>this is a multimap of tagged strings</pre>

==Cycle through the map in the reverse direction==

<source lang="cpp">#include <iostream>
#include <string>
#include <map>
#include <utility>
using namespace std;
void show(const char *msg, map<string, string> mp);
int main() {
map<string, string> phonemap;
phonemap["A"] = "444-555-1234";
phonemap["B"] = "555-555-6576";
phonemap["C"] = "555-555-9843";
show("Here is the original map: ", phonemap);
phonemap["B"] = "555 555-5555";
cout << "New number: " << phonemap["B"] << endl;
// Cycle through the map in the reverse direction.
map<string, string>::reverse_iterator ritr;
cout << "Display phonemap in reverse order:" << endl;
for(ritr = phonemap.rbegin(); ritr != phonemap.rend(); ++ritr)
cout << ritr->first << ": " << ritr->second << endl;
return 0;
}
// Display the contents of a map<string, string> by using an iterator.
void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr;
cout << msg << endl;
for(itr=mp.begin(); itr != mp.end(); ++itr)
cout << " " << itr->first << ": " << itr->second << endl;
cout << endl;
}</source>

==Declare an iterator to a map<string, int>==

<source lang="cpp">#include <iostream>
#include <string>
#include <map>
using namespace std;
int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
// Declare an iterator to a map<string, int>.
map<string, int>::iterator itr;
// Display the first element in m.
itr = m.begin();
cout << "Here is the first key/value pair in m: "
<< itr->first << ", " << itr->second << endl;
return 0;
}</source>

==Declare a reverse iterator to a map<string, itr>==

<source lang="cpp">#include <iostream>
#include <string>
#include <map>
using namespace std;
int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
// Declare an iterator to a map<string, int>.
map<string, int>::iterator itr;
// Declare a reverse iterator to a map<string, itr>.
map<string, int>::reverse_iterator ritr;
// show the contents of m in reverse order.
cout << "The contents of m in reverse:\n";
for(ritr=m.rbegin(); ritr != m.rend(); ++ritr)
cout << " " << ritr->first << ", " << ritr->second << endl;
cout << endl;

return 0;
}</source>

==Display the first element in map==

<source lang="cpp">#include <iostream>
#include <string>
#include <map>
using namespace std;
int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
// Declare an iterator to a map<string, int>.
map<string, int>::iterator itr;
// Display the first element in m.
itr = m.begin();
cout << "Here is the first key/value pair in m: "
<< itr->first << ", " << itr->second << endl;
return 0;
}</source>

==Display the last element in map==

<source lang="cpp">#include <iostream>
#include <string>
#include <map>
using namespace std;
int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
// Declare an iterator to a map<string, int>.
map<string, int>::iterator itr;
// Display the last element in m.
itr = m.end();
--itr;
cout << "Here is the last key/value pair in m: "
<< itr->first << ", " << itr->second << "\n\n";

return 0;
}</source>

==Loop through map and print all the key/value pair==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
#include <map> // map class-template definition
int main()
{
std::map< int, double, std::less< int > > pairs;
pairs.insert( std::map< int, double, std::less< int > >::value_type( 15, 2.7 ) );
pairs.insert( std::map< int, double, std::less< int > >::value_type( 30, 111.11 ) );
pairs.insert( std::map< int, double, std::less< int > >::value_type( 0, 1010.1 ) );
pairs.insert( std::map< int, double, std::less< int > >::value_type( 10, 22.22 ) );
pairs.insert( std::map< int, double, std::less< int > >::value_type( 25, 33.333 ) );
pairs.insert( std::map< int, double, std::less< int > >::value_type( 0, 77.54 ) ); // dup ignored
pairs.insert( std::map< int, double, std::less< int > >::value_type( 20, 9.345 ) );
pairs.insert( std::map< int, double, std::less< int > >::value_type( 15, 99.3 ) ); // dup ignored
cout << "pairs contains:\nKey\tValue\n";
// use const_iterator to walk through elements of pairs
for ( std::map< int, double, std::less< int > >::const_iterator iter = pairs.begin();
iter != pairs.end(); ++iter )
cout << iter->first << "\t" << iter->second << "\n";
cout << endl;
return 0;
}</source>
<pre class=codeResult>pairs contains:
Key Value
0 1010.1
10 22.22
15 2.7
20 9.345
25 33.333
30 111.11</pre>

==reverse_iterator from map==

<source lang="cpp">#include <iostream>
#include <string>
#include <map>
#include <utility>
using namespace std;
void show(const char *msg, map<string, string> mp);
int main() {
map<string, string> phonemap;
phonemap["A"] = "444-555-1234";
phonemap["B"] = "555-555-6576";
phonemap["C"] = "555-555-9843";
show("Here is the original map: ", phonemap);
cout << endl;
phonemap["B"] = "555 555-5555";
cout << "New number for B: " << phonemap["B"] << endl;
// Use find() to find a number.
map<string, string>::iterator itr;
itr = phonemap.find("A");
if(itr != phonemap.end())
cout << "Number for A is " << itr->second << endl;
// Cycle through the map in the reverse direction.
map<string, string>::reverse_iterator ritr;
cout << "Display phonemap in reverse order:" << endl;
for(ritr = phonemap.rbegin(); ritr != phonemap.rend(); ++ritr)
cout << " " << ritr->first << ": " << ritr->second << endl;
cout << endl;
return 0;
}
// Display the contents of a map<string, string> by using an iterator.
void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr;
cout << msg << endl;
for(itr=mp.begin(); itr != mp.end(); ++itr)
cout << " " << itr->first << ": " << itr->second << endl;
cout << endl;
}</source>

==Use iterator to loop through map and print all elements==

<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
/* type of the container:
* - map: elements key/value pairs
* - string: keys have type string
* - float: values have type float
*/
typedef map<string,float> StringFloatMap;
StringFloatMap coll;
// insert some elements into the collection
coll["VAT"] = 0.15;
coll["Pi"] = 3.1415;
coll["an arbitrary number"] = 4983.223;
coll["Null"] = 0;
/* print all elements
* - iterate over all elements
* - element member first is the key
* - element member second is the value
*/
StringFloatMap::iterator pos;
for (pos = coll.begin(); pos != coll.end(); ++pos) {
cout << "key: \"" << pos->first << "\" "
<< "value: " << pos->second << endl;
}
}</source>
<pre class=codeResult>key: "Null" value: 0
key: "Pi" value: 3.1415
key: "VAT" value: 0.15
key: "an arbitrary number" value: 4983.22</pre>

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