Tikz - 无法弄清楚为什么我的线路无法连接

Question

我不明白为什么我的代码不能编译成所附的图像，不确定我是否遗漏了 Tikz 工作原理中的某些内容或者存在其他问题：

代码

\begin{tikzpicture}
        \node[shape=circle,draw=black] (1) {$1$};
        \node[shape=circle,draw=black] (2) [right of=1] {$2$};
        \node[shape=circle,draw=black] (3) [below of=1] {$3$};
        \node[shape=circle,draw=black] (4) [right of=3] {$4$};
        \path[]
        (4) edge [loop below] node (4)
        (1) [-] edge node[right] (2)
        (1) [-] edge node[below] (3)
        (2) [-] edge node[above] (3);
    \end{tikzpicture}

它应该是什么样子

它看起来像什么

Answer 1

路径中存在不必要的节点。（celi 解决了他们的答案通过添加{}，这可以使代码编译但添加似乎未被使用的节点。）

\documentclass[border=3.14mm,tikz]{standalone}
\begin{document}
\begin{tikzpicture}
        \node[shape=circle,draw=black] (1) {$1$};
        \node[shape=circle,draw=black] (2) [right of=1] {$2$};
        \node[shape=circle,draw=black] (3) [below of=1] {$3$};
        \node[shape=circle,draw=black] (4) [right of=3] {$4$};
        \path[]
        (4) edge [loop below] (4)
        (1) [-] edge  (2)
        (1) [-] edge  (3)
        (2) [-] edge  (3);
\end{tikzpicture}
\end{document}

Answer 2

这对我有用：

\begin{tikzpicture}
\node[shape=circle,draw=black] (1) {$1$};
\node[shape=circle,draw=black] (2) [right of=1] {$2$};
\node[shape=circle,draw=black] (3) [below of=1] {$3$};
\node[shape=circle,draw=black] (4) [right of=3] {$4$};
\path (1) edge [] node [left] {} (2)
(1) edge [] node [below] {} (3)
(2) edge [] node [above] {} (3)
(4) edge [loop above] node[] {} (4);
\end{tikzpicture}