在树中添加一个节点

Question

问题：

我有一棵 MWE 树，我想在 G 下添加一个带有标签 I 的节点。该怎么做？

\documentclass[10pt]{article}
\usepackage{pgf,tikz,pgfplots}
\pgfplotsset{compat=1.15}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\pagestyle{empty}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{center}
    \begin{tikzpicture}
    \node [circle,draw]{F} [level distance=10mm,sibling distance=25mm]
    child { node [circle,draw]{D} [level distance=10mm ,sibling distance=15mm]
        child {node [circle,draw] {B}
            child {node [circle,draw] {A}}
            child {node [circle,draw]{C}}}
        child {node [circle,draw]{E}}
    }
    child {node [circle,draw] {J} [level distance=10mm ,sibling distance=15mm]
        child {node [circle,draw] {G}}
        child {node [circle,draw]{K}}
    };
\end{tikzpicture}
\end{center}    

\end{document}

Answer 1

像这样：

\documentclass[10pt]{article}
\usepackage{tikz}

\pagestyle{empty}
\begin{document}
\begin{center}
    \begin{tikzpicture}
    \node [circle,draw]{F} [level distance=10mm,sibling distance=25mm]
    child { node [circle,draw]{D} [level distance=10mm ,sibling distance=15mm]
        child {node [circle,draw] {B}
            child {node [circle,draw] {A}}
            child {node [circle,draw]{C}}}
        child {node [circle,draw]{E}}
    }
    child {node [circle,draw] {J} [level distance=10mm ,sibling distance=15mm]
        child {node [circle,draw] {G}
            child {node [circle, draw] {I}}  % <--- added node
                }
        child {node [circle,draw]{K}}
    };
\end{tikzpicture}
\end{center}    

\end{document}

附录： 根据您的评论的解决方案（如果我理解正确的话）：

\documentclass[10pt]{article}
\usepackage{tikz}

\begin{document}
    \begin{center}
\begin{tikzpicture}
    \node [circle,draw]{F} [level distance=10mm,sibling distance=25mm]
    child { node [circle,draw]{D} [level distance=10mm ,sibling distance=15mm]
        child {node [circle,draw] {B}
            child {node [circle,draw] {A}}
            child {node [circle,draw]{C}}}
        child {node [circle,draw]{E}}
    }
    child {node [circle,draw] {J} [level distance=10mm ,sibling distance=15mm]
        child {node [circle,draw] {G}
            child[missing]                  % <--- added node
            child {node [circle, draw] {I}} % <--- added node
                }
        child {node [circle,draw]{K}}
    };
\end{tikzpicture}
    \end{center}    
\end{document}

使用forest包的替代解决方案：

\documentclass{article}
\usepackage{forest}

\begin{document}
\begin{center}
    \begin{forest}
for tree = {
    circle,
    draw,
    minimum size=1.5em,
    inner sep=2pt,
    s sep+=4mm
            }
[F
    [D
        [B
            [A]
            [C]
        ]
        [E]
    ]
    [J,fit=band
        [G
            [,phantom]
            [I]
        ]
        [K]
    ]
]
    \end{forest}
\end{center}
 \end{document}

得出类似的结果：