digraph huffman {
  node [fontname="DejaVuSans"];
  edge [fontname="DejaVuSans"];
  margin = "0";
  rankdir = "LR";

  start [shape=circle,label="start"];
  start -> n0 [label="0"];
  start -> n1 [label="1"];
  n0 [shape=circle,label=""];
  n0 -> n00 [label="0"];
  n0 -> n01 [label="1"];
  n00 [shape=circle,label=""];
  n00 -> n000 [label="0"];
  n00 -> n001 [label="1"];
  n000 [shape=record,label="{1|1}"];
  n001 [shape=record,label="{0|1}"];
  n01 [shape=record,label="{1|0}"];
  n1 [shape=record,label="{0|0}"];
}
