如何获取树状结构图

Question

我想在 Latex 中获得上面显示的树状图，但我不知道如何编辑它。我试图按照以下方式构建此图，但结果与原始图片不一样。我面临的问题是：

1. 不知道如何调整同一层级下两个节点之间的距离；
2. 我不知道如何像原始图片中那样装饰圆圈。

任何帮助将不胜感激。

\documentclass{article}
\usepackage{forest, color}
\usepackage{adjustbox}
\begin{document}
% Globally set style for your trees 
\forestset{circles/.style={for tree={circle,draw, text width =1em,text centered,edge=->}}}
\begin{adjustbox}{valign=m}
  \begin{forest}
    circles
    [{$f$}
      [{$e$}]
      [{$f$}
         [{$x$}]
         [{$i$}
            [{$x$}]
         ]
      ]
    ] 
  \end{forest}
\end{adjustbox}

Answer 1

不清楚您所说的“装饰”是指图像的哪些方面。我假设是节点左上方/右上方的标签。代码中带有注释，解释了如何增加级别和兄弟节点之间的距离、如何使节点大小统一以及如何在相关位置添加标签。

\documentclass[border=10pt]{standalone}
\usepackage{forest}
\forestset{
  circles/.style={
    for tree={
      math content,
      circle,
      draw,
      text width=1em,
      text centered,
      edge=->,
      s sep'+=5pt, % increase distance between siblings by 5pt
      l sep'+=5pt, % increase distance between levels by 5pt
    },
    before typesetting nodes={
      for tree={% make circles uniform in size
        content/.wrap value=\strut ##1,
        % split content of nodes into content and value for my label
        split option={content}{:}{content,my label},
      },
    },
  },
  my label/.style={% put the label left or right, depending on which child and level we have
    label/.process={On=On=|? {n'}{1} {level}{0} {45:$#1$}{135:$#1$}},
  },
}
\begin{document}
\begin{forest}
  circles
  [f:\epsilon
    [e:1]
    [f:2
       [x:21]
       [i:22
          [x:221]
       ]
    ]
  ]
\end{forest}
\end{document}

如果你本质上是在数树（除了根节点），你甚至不需要指定标签。你可以用类似下面的代码实现相同的结果

\documentclass[border=10pt]{standalone}
\usepackage{forest}
\forestset{
  circles/.style={
    for tree={
      math content,
      circle,
      draw,
      text width=1em,
      text centered,
      edge=->,
      s sep'+=5pt, % increase distance between siblings by 5pt
      l sep'+=5pt, % increase distance between levels by 5pt
    },
    before typesetting nodes={
      for tree={% make circles uniform in size
        content/.wrap value=\strut ##1,
        if level=0{
          my label=\epsilon,
        }{
          temptoksa=,
          for nodewalk={filter={reverse={current and ancestors}}{>On>{level}{0}}}{temptoksa+/.option=n},
          my label/.register=temptoksa,
        },
      },
    },
  },
  my label/.style={% put the label left or right, depending on which child and level we have
    label/.process={On=On=|? {n'}{1} {level}{0} {45:$#1$}{135:$#1$}},
  },
}
\begin{document}
\begin{forest}
  circles
  [f
    [e]
    [f
       [x]
       [i
          [x]
       ]
    ]
  ]
\end{forest}
\end{document}

为了比较：