代码

digraph BalancedBinaryTree {
    node [fontname="Arial", shape=circle, style=filled, color="#ffffff", fillcolor="#0077be", fontsize=12, width=0.7, height=0.7];
    edge [fontname="Arial", fontsize=10, color="#333333", arrowsize=0.5];

    // 定义节点
    node1 [label="1"];
    node2 [label="2"];
    node3 [label="3"];
    node4 [label="4"];
    node5 [label="5"];
    node6 [label="6"];
    node7 [label="7"];
    node8 [label="8"];
    node9 [label="9"];
    node10 [label="10"];
    node11 [label="11"];
    node12 [label="12"];
    node13 [label="13"];
    node14 [label="14"];
    node15 [label="15"];

    // 连接节点
    node1 -> {node2, node3};
    node2 -> {node4, node5};
    node3 -> {node6, node7};
    node4 -> {node8, node9};
    node5 -> {node10, node11};
    node6 -> {node12, node13};
    node7 -> {node14, node15};
}

效果