DeepSeek R1 AI Test code piece

deepseek-r1-test.cs

// For YouTube video:
// https://youtu.be/UnPZHwVCQdo
public IEnumerable<T> Flatten(T parent)
    where T : IParent
{
    yield return parent;
    
    foreach (T child in parent.Children)
    {
        foreach (T grand in Flatten(child))
            yield return grand;
    }
}