Stereogram of a zig-zag tensegrity dodecahedron trapped in a bowl-like, 'non-inflated' configuration. |
For this reason, it may be best to prioritize doing as many shuffle edits as early as possible. The plan would be to reach the final, sturdy, maximum-volume configuration through a growing sequence of structures that are themselves sturdy and maximum-volume.
Recall that an undip word is a shuffle of two Dyck words: an up-word and a down-word. Dyck words are formed by insertion edits alone—there is no shuffling of the parentheses past each other. Thus, in the generation of a Dyck word, when a parenthesis pair, '()', is inserted at the correct location for the open-parenthesis, the close-parenthesis is also, automatically, in the correct position.
The rule is the same for an undip word when the up-word/down-word is considered in isolation: if the just-inserted u/n is in the correct location, the adjacent d/p is also in the correct location. However, it might be necessary to translate the adjacent d/p to the right, shuffling past some characters of the other kind. This should be done immediately after insertion by following the insertion with a sequence of shuffles until the d/p is correctly interleaved with the characters of the other kind. Only then would more insertions be possible on that orbit of the Hamilton circuit.
Example:
|u|.ns = undp
The growth sequence above builds a ud 3-strut tensegrity in the first orbit, inserts an np 'ear' (a spliced-in triangular envelope) to form a unpd quad envelope during the second orbit, and immediately shuffles its p to the right, completing a undp tetrahedron in two orbits.
The shuffle-greedy strategy settles how all shuffle edits will be done: all letters present in the undip word will be correctly interleaved at the conclusion of each orbit. We still need a strategy for choosing which insertion to prioritize when insertions are possible. Of course, within the two Dyck words we must follow the Dyck rules and insert the lowest-order parentheses first. But strategic decisions may remain.
The simplest strategy would be to do the first possible Dyck-rule insertion that presents itself (be it up or down.) Though we need to maintain a reasonable balance of up-words and down-words to have sturdy intermediate structures, this may be something that can be left to chance.
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