how to use map in c++? code example

Example 1: map declaration c++

//assuming your variables are called : variables_
#include <map>
#include <string>

std::map<int, std::string> map_;
map_[1] = "mercury";
map_[2] = "mars";
map_.insert(std::make_pair(3, "earth"));
//either synthax works to declare a new entry

return map_[2]; //here, map_[2] will return "mars"

Example 2: map of maps c++

map <typename,map<typename,typename>> mp;
map[key1][key2]=values

Example 3: basic ex of maps in c++

#include <iostream> 
#include <iterator> 
#include <map> 
   
using namespace std; 
   
int main() 
{ 
     map<int, int> marks; 
     marks.insert(pair<int, int>(160, 42)); 
     marks.insert(pair<int, int>(161, 30)); 
     marks.insert(pair<int, int>(162, 40)); 
     marks.insert(pair<int, int>(163, 50)); 
     marks.insert(pair<int, int>(164, 31)); 
     marks.insert(pair<int, int>(165, 12)); 
     marks.insert(pair<int, int>(166, 34)); 
   
     map<int, int>::iterator itr; 
     cout << "nThe map marks is : n"; 
     cout << "ROLL NO.tMarksn"; 
     for (itr =  marks.begin(); itr !=  marks.end(); ++itr) { 
        cout  << itr->first 
             << "t   t" << itr->second << 'n'; 
     } 
     cout << endl; 
     return 0;     
  }