Turn some land squares into sea such that,
- all sea squares are connected to each other through other sea squares orthogonally,
- no two land squares are adjacent orthogonally and
- it is impossible to turn a sea square to land while still satisfying the above two conditions.
A number outside the grid indicates the number of land squares remaining in the corresponding row/column.
(Rules and example from WPC 2017 IB)
History of the puzzle
Invented by Ivan Koswara (Indonesia) in 2017 as a submission for Puzzle Innovations Contest, a pre-event of WPC 2017. The puzzle was inspired by maximality conditions, common in combinatorics.
Appearances in the past WPCs
- WPC 2017/Round 18 by Ashish Kumar