parent node (in a tree)ParentNodeInATree2002-03-02 11:52:562002-03-02 13:06:57Definition\usepackage{amssymb}
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%\usepackage{graphicx}
\usepackage{xypic}
\xyoption{all}
\usepackage{color}A \emph{parent} node $P$ of a node $C$ in a tree is the first node which lies along the path from $C$ to the root of the tree, $R$.
Drawn in the canonical root-at-top manner, the parent node of a node $C$ in a tree is simply the node immediately above $C$ which is connected to it.
\begin{center}
$$\xymatrix{
& \bullet \ar@{-}[dl] \ar@{-}[dr] & & & \\
\bullet & & {\color{red}\bullet} \ar@{-}[dr]\ar@{-}[dl] & & \\
& \bullet \ar@{-}[dl] & & {\color{blue}\bullet} & \\
\bullet & & & & }$$
{\tiny Figure: A node (blue) and its parent (red.)}
\end{center}