redblack.tex

\documentclass[margin=0.5cm]{standalone}

\usepackage{varwidth}

%
% Cooper Pierce <cppierce@andrew.cmu.edu>
%
% For use in the book,
%   1. compile with latexmk,
%   2. use dvisvgm
% E.g., latexmk redblack
%   && dvisvgm --no-fonts --clipjoin --bbox=papersize redblack
%   && mv redblack-1.svg redblack.svg
% (for whatever reason my version of pdflatex makes a two page dvi)
%
%

\usepackage{tikz}
\usetikzlibrary{arrows}
\usepackage{forest}

\begin{document}
    \pagecolor{white}
    \tikzset{%
        /forest,
        forest node/.style={circle, inner sep=0pt, text centered},
        arn n/.append style={
            text=white,
            font=\sffamily\bfseries,
            draw=black,
            fill=black,
            text width=1.5em,
        },
        arn r/.append style={%
            text=white,
            font=\sffamily\bfseries,
            draw=red,
            fill=red,
            text width=1.5em,
        },
    }

    \forestset{%
        default preamble={
            for tree={
                font=\sffamily,
                forest node,
                edge path={
                    \noexpand\path[color=black, -stealth', \forestoption{edge}]
                    (!u.parent anchor) -- (.child anchor)\forestoption{edge label};
                },
                l sep+=.25cm,
                s sep+=.25cm,
                fit=band,
            }
        }
    }
    \begin{varwidth}{\textwidth}
    \begin{forest}
        [, arn n
            [, arn r
                [+, arn r,
                    [a]
                    [b]
                ]
                [c]
            ]
            [d]
        ]
        \node at (current bounding box.north west)
            [draw,aspect=6]
            {\emph{Case 1}};
    \end{forest}\hspace{3em}
    \begin{forest}
        [, arn n
            [, arn r
                [a]
                [+, arn r,
                    [b]
                    [c]
                ]
            ]
            [d]
        ]
        \node at (current bounding box.north west)
            [draw,aspect=6]
            {\emph{Case 2}};
    \end{forest}
    \vspace{2em}

    \begin{forest}
        [, arn n
            [a]
            [, arn r
                [b]
                [+, arn r,
                    [c]
                    [d]
                ]
            ]
        ]
        \node at (current bounding box.north east)
            [draw,aspect=6]
            {\emph{Case 3}};
    \end{forest}\hspace{3em}
    \begin{forest}
        [, arn n
            [a]
            [, arn r
                [+, arn r,
                    [b]
                    [c]
                ]
                [d]
            ]
        ]
        \node at (current bounding box.north east)
            [draw,aspect=6]
            {\emph{Case 4}};
    \end{forest}
    \end{varwidth}
\end{document}