How to iterate over a map of set (std::map<string,std::set< string> >) in C++?

Question

For a particular key I want to insert and print elements of the set corresponding to that key. For, eg if I have A - Orange, apple B - Red, blue

How do I print this? So far I have written this:`

std::map<string,std::set<string> > mp;
std::map<string,std::set<string> >::const_iterator row;
std::set<string>:: const_iterator col;

mp["A"].insert("pawan");
mp["A"].insert("patil");

for (row = mp.begin(); row!= mp.end(); row++)
    for (col = row->begin(); col!=row.end(); col++)
return 0;`

I don't know how to begin. Please help!`

Answer 1

for(auto const& pair : mp) {
    cout << pair.first << ": ";
    for(auto const& elem : pair.second) {
        cout << elem << ", ";
    }
    cout << "\n";
}

live example

Or, if you want to use std algorithms more:

std::for_each(mp.cbegin(), mp.cend(), [](auto const& pair){
    cout << pair.first << ": ";
    std::copy(pair.second.cbegin(), pair.second.cend(), std::ostream_iterator<std::string>(std::cout, ", "));
    cout << "\n";
});

live example

Answer 2

The question wants to insert an element, and then print the set for that key only.

The first step is to find the set:

auto &s=mp["A"];

Now, insert values into this set:

s.insert("pawan");
s.insert("patil");

And now, iterate over the set, printing the values in the set:

for (const auto &v:s)
    std::cout << v << std::endl;

Answer 3

for(auto it=mp.begin();it!=mp.end();++it)  //Loop to iterate over map elements
 {
    cout<<it->first<<"=";    
    for(auto it1=it->second.begin(); it1 !=it->second.end(); it1++)
        cout<<*it1<<" ";
    cout<<"\n";   
}

The outer for loop iterates over all the elements of map and Inner for loop prints the value corresponding to set associated with the key in the map.