How can I draw a rooted tree structure graph? [duplicate]

Question

I just started doing things with TikZ today and I don't know how to draw a graph which should look like this:

Can someone please help me?

Answer 1

As suggested @Alan Munn in his comments, your tree can be simple drawn by use of forest package. For example, the code for the first tree can be:

\documentclass[border=3.141592]{standalone}
\usepackage{forest}
\usetikzlibrary{arrows.meta}

\begin{document}
\begin{forest}
  for tree={
    edge = {Stealth-},
    grow = south
            }
[ \^{I}
    [2\^{I}, 
      [21\^{I}]
      [22\^{I}]
    ]
    [3\^{I},
      [31\^{I}]
      [32\^{I}]
    ]
]
\end{forest}
\end{document}

Information about forest you can found in the package documentation.