The Complexity of Clickomania
<|reference_start|>The Complexity of Clickomania: We study a popular puzzle game known variously as Clickomania and Same Game. Basically, a rectangular grid of blocks is initially colored with some number of colors, and the player repeatedly removes a chosen connected monochromatic group of at least two square blocks, and any blocks above it fall down. We show that one-column puzzles can be solved, i.e., the maximum possible number of blocks can be removed, in linear time for two colors, and in polynomial time for an arbitrary number of colors. On the other hand, deciding whether a puzzle is solvable (all blocks can be removed) is NP-complete for two columns and five colors, or five columns and three colors.<|reference_end|>
@article{biedl2001the,
    title={The Complexity of Clickomania},
    author={Therese C. Biedl, Erik D. Demaine, Martin L. Demaine, Rudolf
  Fleischer, Lars Jacobsen, J. Ian Munro},
    journal={arXiv preprint arXiv:cs/0107031},
    year={2001},
    archivePrefix={arXiv},
    eprint={cs/0107031},
    primaryClass={cs.CC cs.DM cs.DS}
}