Shikaku (Divide by Box) partitions the grid into rectangles. Each rectangle contains one number equal to its area. Factorisation determines shape options—prime clues force 1×n. Created by a Kyoto University maths student.
ルール
Partition the grid into non-overlapping rectangles. Each rectangle contains exactly one clue; its area must equal that number. Rectangles share edges only; every cell belongs to one rectangle. Prime-number clues force 1×n shapes. Solve by logic; unique solution. Clue of 1 is a 1×1; large clues near edges constrain orientation; adjacent clues of incompatible sizes force a boundary. Factorisation determines shape options.
歴史
Shikaku was created by Yoshinao Anpuku, a Kyoto University maths student, and published in Nikoli in 1989. "Divide by Box" is the common English name. NP-complete. Strong connection to maths education (factors, area). Spread to international puzzle books and apps such as Conceptis Shikaku. The Nikoli origin story is well known in puzzle communities.
戦略のヒント
Factorise each clue to see rectangle options; prime clues have only one shape. Solve large clues near edges first—orientation often forced. Small clues near each other constrain boundaries.
文化的背景
Maths education connection (factors, area); Nikoli origin story; NP-complete; digital puzzle apps. Shikaku was created by Yoshinao Anpuku, a Kyoto University maths student, in 1989. Factorisation determines rectangle shapes; prime clues force 1×n. The puzzle rewards spatial reasoning and factor knowledge. Available on Nikoli.com, Conceptis Shikaku, and Simon Tatham's Portable Puzzle Collection.
購入・プレイ
- Shikaku Puzzle Book (Nikoli) Official Nikoli shikaku collection
- Play Shikaku free in browser (Simon Tatham — Rectangles) Free, open-source browser implementation