如何在 tikz 中创建功能图？

Question

    \begin{tikzpicture}[
            every node/.style={on grid},
            setA/.style={circle,inner sep=2pt},
            every fit/.style={draw,ellipse,text width=25pt},
            >=latex
            ]

            % set A
            \node[setA, label=$1$] (a) {};
            \node [below = of a,label=$3$] (b) {};
            \node [below = of b,label=$5$] (c) {};
            \node[above=of a] {$A$};

            % set B
            \node[inner sep=0pt,right=3cm of a] (x) {$5$};
            \node[inner sep=0pt,below = of x] (y) {$12$};
            \node[inner sep=0pt,below = of y] (z) {$8$};
            \node[above=of x] {$B$};

            % the arrows
            \draw[->,shorten >= 3pt] (a) -- node {} (x);
            \draw[->,shorten >= 3pt] (b) -- node {} (y);
            \draw[->,shorten >= 3pt] (c) -- node {} (z);

            % the boxes around the sets
            \begin{pgfonlayer}{background}
            \node[fit= (a) (c) ] {};
            \node[fit= (x) (z) ] {};
            \end{pgfonlayer}
            \end{tikzpicture}

此代码创建了一个函数图。问题在于集合 A 的元素应该位于下方，与集合 B 的元素一样对齐。请帮我修复这些问题。谢谢！

Answer 1

如果您想涵盖不同的情况，您的代码就不是很通用且调整起来很繁琐。

以下代码解决了您的情况并且更容易调整：

\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{fit, shapes}

\begin{document}

\begin{tikzpicture}
    \foreach[count=\i] \lseti/\lsetmi in {{A}/{1,3,5},{B}/{5,12,8}} {
        \begin{scope}[local bounding box=\lseti, x=3cm, y=1cm]
            \foreach[count=\j] \lj in \lsetmi {
                \node[minimum width=2em] (n-\j-\lseti) at (\i,-\j) {\lj};
            }
        \end{scope}
        \node[ellipse, draw, fit=(\lseti), label={above:$\lseti$}] {};
    }
    \foreach \i in {1,...,3} {
        \draw[->] (n-\i-A) -- (n-\i-B);
    }
\end{tikzpicture}

\end{document}