The build graph is incorrect when build an optimized segment sequence.

In the encoding process, we will construct a graph, and then use the single-source shortest path algorithm to find the optimal segment sequence, but the constructed graph seems to be problematic.

Keep other parameters as default, and then encode "ABCDEF123", you will get the following graph(Byte mode is omitted). The cost from node ("ABCDEF[A]") to node ("123[A]") is 16, which is wrong, it should be 17.