Restore the erased pipes
1 model, chain, 3.4 MB
A 3-by-4 lattice of junctions is joined by 17 one-way pipes, drawn on a 5-by-7 board where junction cells and pipe cells alternate. Each junction cell shows how much liquid it adds or removes, each pipe cell shows how much flows through it, twelve pipe cells have been erased to '?', and the task is to write back a flow of 0 to 4 in every erased cell so that every junction balances exactly.
solved exactly on 100% of held-out instances