Hang the mobile
2 models, chain, 6.6 MB
An instance shows a hanging mobile: a fixed complete binary tree of 7 rods over 8 hooks, where each rod carries an integer arm pair and two of the rods have had their arm pair erased, together with a sorted bag of 8 weights, one per hook. The answer fills in which weight hangs on each hook and the two erased arm pairs, and is correct when the whole bag is used exactly once, every rod balances (left total x left arm = right total x right arm), and every arm pair is in lowest terms.
solved exactly on 100% of held-out instances