Wataridori is a pencil puzzle that involves drawing paths in a rectangular grid to connect circles into pairs while satisfying several constraints. In this paper, we prove that deciding whether a given Wataridori puzzle has a solution is NP-complete via a reduction from Numberlink, another pencil puzzle that has previously been proved NP-complete.
Cite
@article{arxiv.2601.09345,
title = {Wataridori is NP-Complete},
author = {Suthee Ruangwises},
journal= {arXiv preprint arXiv:2601.09345},
year = {2026}
}