Simple and fast string algorithms by Lyndon words

2021 Fiscal Year Annual Research Report

• Project/Area Number: 18K18002
• Research Institution: Kyushu University
• Principal Investigator: 中島 祐人 九州大学, システム情報科学研究院, 助教 (80804682)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 文字列アルゴリズム / 文字列組合せ論

Outline of Annual Research Achievements

本研究課題では，簡潔で高速な文字列処理アルゴリズム開発への新たなアプローチとして，Lyndon 文字列や Lyndon 文字列に基づいたデータ構造の未知の性質を明らかにし，それらを用いたアルゴリズム開発を目的としている．この目的達成のために，Lyndon 文字列に関連するトピックを中心に，様々な文字列処理アルゴリズムに関する問題に令和3年度も引き続き取り組んだ．当初の計画では令和2年度までの3年間を計画していたが，世界的な感染症拡大の影響のために1年間の事業延長を行った．したがって，本年度が最終年度である．最終年度中に一部の研究成果を，6報の論文を査読付き国際会議にて発表，5報の論文を査読付き国際学術雑誌にて公表している．

これらの研究成果は，文字列圧縮索引，文字列検索のための索引構造，文字列の特徴（極小ユニーク文字列，回文，極大繰り返し）抽出アルゴリズム，準動的な文字列処理アルゴリズム，組合せ的性質の解明などのトピックにおける成果であり，文字列情報学分野の多岐にわたる問題を解決しており，いずれも分野の発展に寄与する重要な成果である．本研究課題の核である Lyndon 文字列の数理的性質の解明や，Lyndon 文字列を利用した文字列処理に関してもいくつかの成果を挙げることに成功している．当初計画で想定していた成果が十分に得られているとは言い難いが，本計画に隣接するトピックに関して非常に多くの研究成果を挙げている．また，2021年度より開始した新たな研究課題において，本研究で得られた知見が十分に活きるものである確信している．

Research Products

• [Journal Article] Palindromic trees for a sliding window and its applications (2022)
  • Author(s): Takuya Mieno, Kiichi Watanabe, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Information Processing Letters Volume: 173 Pages: -
  • DOI: 10.1016/j.ipl.2021.106174
  • Peer Reviewed
• [Journal Article] Compressed Communication Complexity of Hamming Distance (2021)
  • Author(s): Shiori Mitsuya, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Algorithms Volume: 14 Pages: -
  • DOI: 10.3390/a14040116
  • Peer Reviewed / Open Access
• [Journal Article] c-trie++: A dynamic trie tailored for fast prefix searches (2021)
  • Author(s): Kazuya Tsuruta, Dominik Koeppl, Shunsuke Kanda, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Information and Computation Volume: - Pages: -
  • DOI: 10.1016/j.ic.2021.104794
  • Peer Reviewed / Open Access
• [Journal Article] Efficiently computing runs on a trie (2021)
  • Author(s): Ryo Sugahara, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Theoretical Computer Science Volume: 887 Pages: 143～151
  • DOI: 10.1016/j.tcs.2021.07.011
  • Peer Reviewed
• [Journal Article] Computing Minimal Unique Substrings for a Sliding Window (2021)
  • Author(s): Takuya Mieno, Yuta Fujishige, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Algorithmica Volume: 84 Pages: 670～693
  • DOI: 10.1007/s00453-021-00864-1
  • Peer Reviewed
• [Journal Article] Counting Lyndon Subsequence (2021)
  • Author(s): Ryo Hirakawa, Yuto Nakashima, Shunsuke Inenaga, Masayuki Takeda
  • Journal Title: Proceedings of the Prague Stringology Conference 2021 Volume: - Pages: 53-60
  • Peer Reviewed / Open Access
• [Journal Article] Position Heaps for Cartesian-Tree Matching on Strings and Tries (2021)
  • Author(s): Akio Nishimoto, Noriki Fujisato, Yuto Nakashima, Shunsuke Inenaga
  • Journal Title: Proceedings of 28th International Symposium on String Processing and Information Retrieval Volume: 12944 Pages: 241-254
  • DOI: 10.1007/978-3-030-86692-1_20
  • Peer Reviewed
• [Journal Article] On the Approximation Ratio of LZ-End to LZ77 (2021)
  • Author(s): Takumi Ideue, Takuya Mieno, Mitsuru Funakoshi, Yuto Nakashima, Shunsuke Inenaga, Masayuki Takeda
  • Journal Title: Proceedings of 28th International Symposium on String Processing and Information Retrieval Volume: 12944 Pages: 114-126
  • DOI: 10.1007/978-3-030-86692-1_10
  • Peer Reviewed
• [Journal Article] Grammar Index by Induced Suffix Sorting (2021)
  • Author(s): Tooru Akagi, Dominik Koeppl, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Proceedings of 28th International Symposium on String Processing and Information Retrieval Volume: 12944 Pages: 85-99
  • DOI: 10.1007/978-3-030-86692-1_8
  • Peer Reviewed
• [Journal Article] Longest Common Rollercoasters (2021)
  • Author(s): Kosuke Fujita, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Proceedings of 28th International Symposium on String Processing and Information Retrieval Volume: 12944 Pages: 21-32
  • DOI: 10.1007/978-3-030-86692-1_3
  • Peer Reviewed
• [Journal Article] The Parameterized Suffix Tray (2021)
  • Author(s): Noriki Fujisato, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Journal Title: Proceedings of 12th International Conference on Algorithms and Complexity Volume: 12701 Pages: 258-270
  • DOI: 10.1007/978-3-030-75242-2_18
  • Peer Reviewed
• [Presentation] 文法圧縮索引構造 GCIS-index (2022)
  • Author(s): 赤木 亨, ドミニク クップル, 中島 祐人, 稲永 俊介, 坂内 英夫, 竹田 正幸
  • Organizer: 2021年度 冬のLAシンポジウム
• [Presentation] LZEnd vs LZ77 (2022)
  • Author(s): 井手上 卓弥, 三重野 琢也, 舩越 満, 中島 祐人, 稲永 俊介, 竹田 正幸
  • Organizer: 2021年度 冬のLAシンポジウム
• [Presentation] Counting Lyndon Subsequence (2021)
  • Author(s): Ryo Hirakawa, Yuto Nakashima, Shunsuke Inenaga, Masayuki Takeda
  • Organizer: Prague Stringology Conference 2021
  • Int'l Joint Research
• [Presentation] Position Heaps for Cartesian-Tree Matching on Strings and Tries (2021)
  • Author(s): Akio Nishimoto, Noriki Fujisato, Yuto Nakashima, Shunsuke Inenaga
  • Organizer: 28th International Symposium on String Processing and Information Retrieval
  • Int'l Joint Research
• [Presentation] On the Approximation Ratio of LZ-End to LZ77 (2021)
  • Author(s): Takumi Ideue, Takuya Mieno, Mitsuru Funakoshi, Yuto Nakashima, Shunsuke Inenaga, Masayuki Takeda
  • Organizer: 28th International Symposium on String Processing and Information Retrieval
  • Int'l Joint Research
• [Presentation] Grammar Index by Induced Suffix Sorting (2021)
  • Author(s): Tooru Akagi, Dominik Koeppl, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Organizer: 28th International Symposium on String Processing and Information Retrieval
  • Int'l Joint Research
• [Presentation] Longest Common Rollercoasters (2021)
  • Author(s): Kosuke Fujita, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Organizer: 28th International Symposium on String Processing and Information Retrieval
  • Int'l Joint Research
• [Presentation] The Parameterized Suffix Tray (2021)
  • Author(s): Noriki Fujisato, Yuto Nakashima, Shunsuke Inenaga, Hideo Bannai, Masayuki Takeda
  • Organizer: 12th International Conference on Algorithms and Complexity
  • Int'l Joint Research