我该如何正确乳胶显示我的AVL树？独奏左子挂直降

Question

在下面的代码几乎完美地工作，9，7然而孩子，而不是垂直向下悬挂的作为左子。我怎样才能解决这个？

\usepackage{tikz}
\usepackage{xytree}
\begin{tikzpicture}[level/.style={sibling distance=60mm/#1}]
    \node [circle,draw] {4}
      child {
        node [circle,draw] {2}
            child {node [circle,draw] {1}
       }
        child {
            node [circle,draw]{3}
        }
      }
      child {node [circle,draw] {6}
        child {node [circle,draw]  {5}
        }
      child {node [circle,draw]  {9}
        child {node [circle, draw]  {7}}
      }
    };

\end{tikzpicture}}

谢谢，CB

Answer 1

与所建议的tikz手册协商后，我能够纠正此如下：

\begin{tikzpicture}[level/.style={sibling distance=60mm/#1}]
    \node [circle,draw] {4}
      child {
        node [circle,draw] {2}
            child {node [circle,draw] {1}
       }
        child {
            node [circle,draw]{3}
        }
      }
      child {node [circle,draw] {6}
        child {node [circle,draw]  {5}
        }
      child {node [circle,draw]  {9}
        child {node [circle, draw]  {7}} 
        child [missing]
        }
    };

    \end{tikzpicture}

Answer 2

下面的代码为我工作。它基于你的代码，与所述变化

1）使用tikz库树和 2）单个节点的格式的变化（节点7）

有关的更多信息请参见tikz手册

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{trees}

\begin{document}

\begin{tikzpicture}[level/.style={sibling distance=60mm/#1}]
    \node [circle,draw] {4}
      child {
        node [circle,draw] {2}
            child {node [circle,draw] {1}
       }
        child {
            node [circle,draw]{3}
        }
      }
      child {node [circle,draw] {6}
        child {node [circle,draw]  {5}
        }
      child {node [circle,draw]  {9}
        child[grow via three points={one child at (-1,-1) and two children at (-.5,1) and (.5,1)}] {node [circle, draw]  {7}}
      }
    };

\end{tikzpicture}

\end{document}