// Set implementation and call
// i.e. Returns (creates) the concrete implementation of the object,
// subsequently operation is called on the concrete implementation
ab.Implementor = new ConcreteImplementorA();
ab.Operation();

// Set the context with a strategy
// i.e. Sets the concrete strategy into the context, concrete implementation of the class not
// directly available as a data object (only the algorithm is available).
context = new Context (new ConcreteStrategyA());
context.contextInterface();

// Strategy can be reused instead of creating a new instance every time it is used.
// Sort example
MergeSort mergeSort = new MergeSort();
QuickSort quickSort = new QuickSort();
...
context = new Context (mergeSort);
context.Sort();
...
context = new Context (quickSort);
context.Sort();
...
context = new Context (mergeSort);
context.Sort();

class Sorter abstract
{
   virtual void Sort() = 0;
}

// MergeSorter IS A Sorter
class MergeSorter : public Sorter
{
   virtual void Sort() override;
}

class SortStrategy abstract
{
   virtual void Sort() = 0;
}

// Sorter HAS A SortStrategy
class Sorter
{
   Sorter(SortStragety *strategy) : mStrat(strategy) {}

   void Sort() {mStrat->Sort();}

   SortStrategy *mStrat;
}