MAPSTL

#include<bits/stdc++.h>
using namespace std;

int main() {
    map<int,int>mp;
//   map<int,int> m{ {1,2} , {2,3} , {3,4} }
    //   m.insert( pair<int,int> (4,5));
      //  map <char ,int > mp;
      //  mp[‘b’]  = 1;
    int n;
    cin>>n;
    //INITIALISE MAP
    for(int i=0;i<n;i++)
    { int a,b;
        cin>>a>>b;
       // mp.insert(make_pair(a,b));
        mp.insert({a,b});
        //mp[a[i]]++;
       // mp[i]=make_pair(a,b); cannot do this,wrong way of initialisation
    }
    //OUTPUT MAP;
    map<int,int>::iterator it,it1;
    for(it=mp.begin();it!=mp.end();it++)
    cout<<it->first<<" "<<it->second<<" ";

        for(auto it=mp.begin();it!=mp.end();it++)
    cout<<it->first<<" "<<it->second<<" ";

    for(auto it:mp)
    cout<<it.first<<" "<<it.second<<" ";
    //MAP IN REVERSE ORDER
    map<int,int>::reverse_iterator itr;
    for(itr=mp.rbegin();itr!=mp.rend();itr++)
                cout<<itr->first<<" "<<itr->second << ;

        for(auto itr=v.rbegin();itr!=v.rend();itr++)
                cout<<itr->first<<" " << itr -> second;

    // ERASE FUNCTION
    mp.erase(it) //erase element at iterator position ;
    mp.erase (4);    // remove all elements with key = 4;
    mp.erase(mp.begin(), mp.find(3); //
        mp.erase(it1,it2) //erases element in a range;

        mp.clear(); //clear the map;
        //SORT IN MAP

         // Here if greater<int> is used to make
    // sure that elements are stored in
    // ascending order of keys.
       map<int, string, greater <int> > mymap;

         //values in map are already sort according to their key;
         //if we want to sort it by value then store in a different container;

          map<char,int> map2 (map1.begin(), map1.end());
     /* creates a map map2 which have entries copied
        from map1.begin() to map1.end() */

         map<char,int> map3 (m);
      /* creates map map3 which is a copy of map m */

      mp.empty();
}
    return 0;
}