A C++ set is a bunch of items that are unique and sorted. The good feature about the STL set is that it keeps the set elements sorted. A quick and dirty way to sort a bunch of values is actually to just shove them into the same set. The set will take care of the sorting for you.

We can return to a simple C++ console application for the usage of sets. To use the C++ STL set you need to include <set>, as shown here:

#include <iostream>
#include <set>
using namespace std;

int main()
{
  set<int> intSet;
  intSet.insert( 7 );
  intSet.insert( 7 );
  intSet.insert( 8 );
  intSet.insert( 1 );

  for( set<int>::iterator it = intSet.begin(); it != intSet.end();  ++it )
  {
    cout << *it << endl;
  }
}

The following is the output of the preceding code:

1
7
8

The duplicate 7 is filtered out, and the elements are kept in increasing order inside the set. The way we iterate over the elements of an STL container is similar to UE4's TSet array. The intSet.begin() function returns an iterator that points to the head of the intSet.

The condition to stop iterating is when it becomes intSet.end(). intSet.end() is actually one position past the end of the set, as shown in the following figure:

set<int>::iterator it = intSet.find( 7 );
if( it != intSet.end() )
{
  //  7  was inside intSet, and *it has its value
  cout << "Found " << *it << endl;
}

#include <iostream>
#include <string>
#include <set>
using namespace std;
int main()
{
  set<string> names;
  // so long as we don't have 3 names yet, keep looping,
  while( names.size() < 3 )
  {
    cout << names.size() << " names so far. Enter a name" << endl;
    string name;
    cin >> name;
    names.insert( name ); // won't insert if already there,
  }
  // now print the names. the set will have kept order
  for( set<string>::iterator it = names.begin(); it !=  names.end(); ++it )
  {
    cout << *it << endl;
  }
}

The C++ STL map object is a lot like UE4's TMap object. The one thing it does that TMap does not is to maintain a sorted order inside the map as well. Sorting introduces an additional cost, but if you want your map to be sorted, opting for the STL version might be a good choice.

To use the C++ STL map object, we include <map>. In the following example program, we populate a map of items with some key-value pairs:

#include <iostream>
#include <string>
#include <map>
using namespace std;
int main()
{
  map<string, int> items;
  items.insert( make_pair( "apple", 12 ) );
  items.insert( make_pair( "orange", 1 ) );
  items.insert( make_pair( "banana", 3 ) );
  // can also use square brackets to insert into an STL map
  items[ "kiwis" ] = 44;

  for( map<string, int>::iterator it = items.begin(); it !=  items.end(); ++it )
  {
    cout << "items[ " << it->first << " ] = " << it->second <<  endl;
  }
}

This is the output of the preceding program:

items[ apple ] = 12
items[ banana ] = 3
items[ kiwis ] = 44
items[ orange ] = 1

Notice how the iterator's syntax for an STL map is slightly different than that of TMap: we access the key using it->first and the value using it->second.

Notice how C++ STL also offers a bit of syntactic sugar over TMap; you can use square brackets to insert into the C++ STL map. You cannot use square brackets to insert into a TMap.

#include <iostream>
#include <string>
#include <map>
using namespace std;
int main()
{
  map<string, int> items;
  cout << "Enter 5 items, and their quantities" << endl;
  while( items.size() < 5 )
  {
    cout << "Enter item" << endl;
    string item;
    cin >> item;
    cout << "Enter quantity" << endl;
    int qty;
    cin >> qty;
    items[ item ] = qty; // save in map, square brackets
    // notation
  }

  for( map<string, int>::iterator it = items.begin(); it !=  items.end(); ++it )
  {
    cout << "items[ " << it->first << " ] = " << it->second <<  endl;
  }
}