![偏序集的图表](https://linux22.com/image/469669/%E5%81%8F%E5%BA%8F%E9%9B%86%E7%9A%84%E5%9B%BE%E8%A1%A8.png)
答案1
有很多方法。以下是可能的tikz-cd
\documentclass{article}
\usepackage{tikz-cd, amssymb}
\usetikzlibrary{shapes.geometric}
\tikzcdset{arrow style=tikz, diagrams={>={Triangle[open, length=2mm]}}}
\begin{document}
\begin{tikzcd}[cells={nodes={draw, ellipse, inner sep=0pt, minimum width=12mm, minimum height=8mm}}]
& \{x,y,z\}\\
\{x,y\}\arrow{ur} & \{x,z\}\arrow{u} & \{y,z\}\arrow{ul}\\
\{x\}\arrow{u}\arrow{ur} & \{y\}\arrow{ul}\arrow{ur} & \{z\}\arrow{ul}\arrow{u}\\
& \varnothing\arrow{ul}\arrow{u}\arrow{ur}
\end{tikzcd}
\end{document}