C++ Program to Implement Map in STL

C++Server Side ProgrammingProgramming

A Map is an associative container that store elements in a mapped fashion. Each element has a key value and a mapped value. No two mapped values can have same key values.

Functions are used here:

  • m::find() – Returns an iterator to the element with key value ‘b’ in the map if found, else returns the iterator to end.

  • m::erase() – Removes the key value from the map.

  • m:: equal_range() – Returns an iterator of pairs. The pair refers to the bounds of a range that includes all the elements in the container which have a key equivalent to key.

  • m insert() – To insert elements in the map container.

  • m size() – Returns the number of elements in the map container.

  • m count() – Returns the number of matches to element with key value ‘a’ or ‘f’ in the map.

Example Code

#include<iostream>
#include <map>
#include <string>
using namespace std;
int main () {
   map<char, int> m;
   map<char, int>::iterator it;
   m.insert (pair<char, int>('a', 10));
   m.insert (pair<char, int>('b', 20));
   m.insert (pair<char, int>('c', 30));
   m.insert (pair<char, int>('d', 40));
   cout<<"Size of the map: "<< m.size() <<endl;
   cout << "map contains:\n";
   for (it = m.begin(); it != m.end(); ++it)
      cout << (*it).first << " => " << (*it).second << '\n';
   for (char c = 'a'; c <= 'd'; c++) {
      cout << "There are " << m.count(c) << " element(s) with key " << c << ":";
      map<char, int>::iterator it;
      for (it = m.equal_range(c).first; it != m.equal_range(c).second; ++it)
         cout << ' ' << (*it).second;
         cout << endl;
   }
   if (m.count('a'))
      cout << "The key a is present\n";
   else
      cout << "The key a is not present\n";
   if (m.count('f'))
      cout << "The key f is present\n";
   else
      cout << "The key f is not present\n";
   it = m.find('b');
   m.erase (it);
   cout<<"Size of the map: "<<m.size()<<endl;
   cout << "map contains:\n";
   for (it = m.begin(); it != m.end(); ++it)
   cout << (*it).first << " => " << (*it).second << '\n';
   return 0;
}

Output

Size of the map: 4
map contains:
a => 10
b => 20
c => 30
d => 40
There are 1 element(s) with key a: 10
There are 1 element(s) with key b: 20
There are 1 element(s) with key c: 30
There are 1 element(s) with key d: 40
The key a is present
The key f is not present
Size of the map: 3
map contains:
a => 10
c => 30
d => 40
raja
Published on 29-Mar-2019 16:15:46
Advertisements