tikz制作二叉树

\documentclass{article}
\usepackage{ctex}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[
    level distance=2cm, % 层级之间的垂直距离
    level 1/.style={sibling distance=8cm},  % 第一层节点水平间距
    level 2/.style={sibling distance=4cm},  % 第二层节点水平间距
    level 3/.style={sibling distance=2cm}   % 第三层节点水平间距
]
  \node[circle,draw=blue] {1}
    child {node[circle,draw=red] {刘}
      child {node[circle,draw=blue] {4} 
        child {node[circle,draw=blue] {8}}
        child {node[circle,draw=blue] {9}}
        }    
      child {node[circle,draw=blue] {5}
        child {node[circle,draw=blue] {10}}
        child {node[circle,draw=blue] {11}}
      }
    }
    child {node[circle,draw=blue] {3}
      child {node[circle,draw=blue] {6}
        child {node[circle,draw=blue] {12}}
        child {node[circle,draw=blue] {13}
            child {node[circle,draw=blue] {131}}
            child {node[circle,draw=blue] {132}}
        }
      }
      child {node[circle,draw=blue] {7}
        child {node[circle,draw=blue] {14}}
        child {node[circle,draw=blue] {15}}
      }
    };
\end{tikzpicture}

\end{document}