Construction begins with the empty topology assembly on the left. Every possible extension is constructed in a copy of the initial assembly: Node completes path , node completes path , and node completes path , branching the initial assembly into three new assemblies. Path lengths completed by the introduced node and path lengths incompatible with it are marked and not revisited. Nodes and preclude path , while node precludes paths and . Completed paths are shown in blue, precluded paths are greyed out in the corresponding assemblies. Intermediate topology scores are calculated according to the scoring function. On the next iteration construction paths for assemblies and collide, indicated in red. A single copy of the resulting assembly, , is retained. Assembly is separately extended with node . Additional construction sequences, indicated by ellipses, are not shown.