TeXでさくらんぼ計算

result.png

sakurambo.tex

\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{arrows,calc}

\makeatletter

\def\sakurambo#1{%
  \parse@expression#1
}

\def\draw@sakurambo@expression#1#2#3#4#5{%
  $$#1 + \draw@sakurambo{#2}{#3}{#4} = #5$$
}

\def\draw@expression#1#2#3{%
  $$#1 + #2 = #3$$
}

\def\parse@expression#1+#2{%
  \@tempcnta=#1 \@tempcntb=#2
  \advance \@tempcnta by -10
  \advance \@tempcntb by \@tempcnta
  \multiply \@tempcnta by -1
  \ifnum\@tempcntb>0
    \expandafter%
    \draw@sakurambo@expression
      {#1}{#2}{\the\@tempcnta}{\the\@tempcntb}{%
        \@tempcnta=#1
        \advance \@tempcnta by #2
        \the\@tempcnta}
  \else
    \expandafter
    \draw@expression
      {#1}{#2}{%
        \@tempcnta=#1
        \advance \@tempcnta by #2
        \the\@tempcnta}
  \fi
}

\tikzset{
  cherrynode/.style = {circle, white,  draw=black, fill=red},
  cherrybend/.style = {edge from parent path={(\tikzparentnode.south) edge [bend left=15] (\tikzchildnode.north)},
                       very thick},
  no edge/.style = {edge from parent/.append style={draw=none}}
}

\def\draw@sakurambo#1#2#3{%
  \makebox[1em][c]{%
  \begin{tikzpicture}[
      draw=green,
      cherrybend,
      sibling distance=1.5em,
      level distance=3em,
      baseline={([yshift={-\dp\strutbox+0.5pt}]current bounding box.base)}]
    \node {#1}
      child { node [cherrynode] {#2} }
      child { node [cherrynode] {#3} }
    ;
  \end{tikzpicture}
  }
}
\makeatother

\begin{document}

\sakurambo{5+9}
\sakurambo{9+9}

\sakurambo{7+9}
\sakurambo{1+4}

\sakurambo{1+9}
\sakurambo{7+4}

\makeatletter
%\parse@expression7+8
%\temp
%\draw@sakurambo@expression{7}{8}{3}{5}{15}
\makeatother

\end{document}