At the end you have a small group of strands that begin with Austin and end with Elizabeth, have every cityname in their length, and are five citynames long. These strands represent the solution, or equivalent solutions. The answer is read by sequencing the strand. That's how DNA computing works. This represents 16x more energy than the floor set by the second law of thermodynamics.
Computers built by humans waste about a billion times more energy per operation.
DNA stores memory at a density of about 1 bit per cubic nanometer. This is about a trillion times more efficient that videotape. These advantages make it possible to imagine using DNA to attack problems far beyond the reach of anything electronic computers will be able to do for a very long time. This prospect has attracted much interest. The first conference on DNA computing, which was just held at Princeton, attracted 300 people.