与えられた二分決定木を視覚化してください。
\begin{tikzpicture}[%
    level distance = 12mm,
    level 1/.style = {sibling distance=35mm},
    level 2/.style = {sibling distance=25mm},
]
\node[circle] {Root}
    child {node[circle] {A} 
        child {node[circle] {C}}
        child {node[circle] {D}}
    }
    child {node[circle] {B}
        child {node[circle] {E} 
            child {node[circle] {F}}
            child {node[circle] {G} }
        }
        child {node[circle] {H}};
\end{tikzpicture}