Iterate over vector of pair

Solution 1:

There are at least three errors in the loop.

for ( vector < pair<float,pair<int,int>> >::const_iterator it = edges.begin() ; itt != edges.end; it++){
        cout >> it.first;
    }

First of all you have to use edges.end() instead of edges.end. And inside the body there has to be

    cout << it->first;

instead of

    cout >> it.first;

To escape such errors you could write simply

for ( const pair<float, pair<int,int> > &edge : edges )
{
   std::cout << edge.first;
}

Solution 2:

for ( vector < pair<float,pair<int,int>> >::const_iterator it = edges.begin() ; 

     it != edges.end () ;  // Use (), and assuming itt was a typo
     it++)
{
    cout << it->first; // Use -> 
}

Also, you might want to add a custom comparator for std::sort

Solution 3:

C++14 iterators are a lot simpler

for (const auto& pair : edges)
{
    std::cout << pair.first;
}

or

for (const auto& [first, sec] : edges)
{
    std::cout << first;
}