How to pick which side a node is on in a simple binary tree?

Question

In a simple binary tree, I was able to make the graph look right by adding invisible nodes and invisible edges, for instance from:

digraph
{
        vertex_1 [label="A"];
        vertex_2 [label="B"];
        vertex_2 -> vertex_1 [label="Left"];
}

which produces:

to:

digraph
{
        vertex_1 [label="A"];
        vertex_2 [label="B"];
        vertex_0 [style=invis];
        vertex_2 -> vertex_1 [label="Left"];
        vertex_2 -> vertex_0 [style=invis];
}

which produces:

But when I tried that trick with a 4 node graph (it was originally straight up and down) here is what I got:

digraph
{
        vertex_1 [label="A"];
        vertex_2 [label="B"];
        vertex_3 [label="F"];
        vertex_4 [label="G"];
        vertex_01 [style=invis];
        vertex_02 [style=invis];
        vertex_03 [style=invis];
        vertex_4 -> vertex_3 [label="Left"];
        vertex_3 -> vertex_1 [label="Left"];
        vertex_1 -> vertex_02 [style=invis];
        vertex_4 -> vertex_03 [style=invis];
        vertex_3 -> vertex_01 [style=invis];
        vertex_1 -> vertex_2 [label="Right"];
}

which produced:

Obviously I want B to be on the right side of A. I tried switching the order of the invisible edge statement and the actual edge from B to A, like which one came first but that make no difference. How can I tell the program to put a specific node or edge on a specific side?

score 1 · Accepted Answer · answered Apr 22 '16 at 12:54

For the order left to right the node creation order is relevant. A left node must be created before its right sibling.

digraph
{
    vertex_1 [label="A"];
    vertex_02 [style=invis];
    vertex_2 [label="B"];
    vertex_3 [label="F"];
    vertex_4 [label="G"];
    vertex_01 [style=invis];
    vertex_03 [style=invis];
    vertex_4 -> vertex_3 [label="Left"];
    vertex_3 -> vertex_1 [label="Left"];
    vertex_1 -> vertex_02 [style=invis];
    vertex_4 -> vertex_03 [style=invis];
    vertex_3 -> vertex_01 [style=invis];
    vertex_1 -> vertex_2 [label="Right"];
}

How to pick which side a node is on in a simple binary tree?

1 Answers1