Sankaku-Tori: An Old Western-Japanese Game Played on a Point Set

  • Takashi Horiyama
  • Masashi Kiyomi
  • Yoshio Okamoto
  • Ryuhei Uehara
  • Takeaki Uno
  • Yushi Uno
  • Yukiko Yamauchi
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8496)


We study a combinatorial game named “sankaku-tori” in Japanese, which means “triangle-taking” in English. It is an old pencil-and-paper game for two players played in Western Japan. The game is played on points on the plane in general position. In each turn, a player adds a line segment to join two points, and the game ends when a triangulation of the point set is completed. The player who completes more triangles than the other wins. In this paper, we consider two restricted variants of this game. In the first variant, the first player always wins in a nontrivial way, and the second variant is NP-complete in general.


Line Segment Maximum Match Winning Strategy Incidence Graph Matching Edge 
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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Takashi Horiyama
    • 1
  • Masashi Kiyomi
    • 2
  • Yoshio Okamoto
    • 3
  • Ryuhei Uehara
    • 4
  • Takeaki Uno
    • 5
  • Yushi Uno
    • 6
  • Yukiko Yamauchi
    • 7
  1. 1.Information Technology CenterSaitama UniversityJapan
  2. 2.International College of Arts and ScienceYokohama City UniversityJapan
  3. 3.Graduate School of Informatics and EngineeringUniversity of Electro-CommunicationsJapan
  4. 4.School of Information ScienceJapan Advanced Institute of Science and TechnologyJapan
  5. 5.National Institute of InformaticsJapan
  6. 6.Graduate School of ScienceOsaka Prefecture UniversityJapan
  7. 7.Graduate School of ISEEKyushu UniversityJapan

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