C++ STL map, rbegin() program example

Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows XP Pro SP2

Header file: Standard

Additional project setting: Set project to be compiled as C++

Project -> your_project_name Properties -> Configuration Properties -> C/C++ -> Advanced -> Compiled As: Compiled as C++ Code (/TP)

Other info:

To do: Using the C++ rbegin() to return an iterator addressing the first element in a reversed map in C++ programming

To show: How to use the C++ map, rbegin() to return an iterator addressing the first element in a reversed map in C++ programming

// C++ STL map, rbegin()

#include <map>

#include <iostream>

using namespace std;

int main(void)

{

// map container

map <int, int> m1;

// map iterators

map <int, int> :: iterator m1_Iter;

map <int, int> :: reverse_iterator m1_rIter;

map <int, int> :: const_reverse_iterator m1_crIter;

// simplify pair<int, int> to Int_Pair

typedef pair <int, int> Int_Pair;

// insert data into the map

m1.insert(Int_Pair(1, 10));

m1.insert(Int_Pair(2, 20));

m1.insert(Int_Pair(3, 9));

m1.insert(Int_Pair(4, 30));

// iterate and print

m1_rIter = m1.rbegin();

cout<<"The first element of the reversed map m1 is "<<m1_rIter->first<<endl;

// begin() can be used to start an iteration through a map in a forward order

cout<<"The map is: ";

for (m1_Iter = m1.begin(); m1_Iter != m1.end(); m1_Iter++)

cout<<m1_Iter->first<<" ";

cout<<endl;

// rbegin() can be used to start an iteration through a map in a reverse order

cout<<"The reversed map is: ";

for (m1_rIter = m1.rbegin(); m1_rIter != m1.rend(); m1_rIter++)

cout<<m1_rIter->first<<" ";

cout<<endl;

// a map element can be erased by dereferencing to its key

m1_rIter = m1.rbegin( );

m1.erase(m1_rIter->first);

m1_rIter = m1.rbegin();

cout<<"After the erase(), the first element in the reversed map is "<<m1_rIter->first<<"."<<endl;

return 0;

}

Output examples:

The first element of the reversed map m1 is 4

The map is: 1 2 3 4

The reversed map is: 4 3 2 1

After the erase(), the first element in the reversed map is 3.

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