Maximal Archipelago

Rules

Turn some land squares into sea such that,

1. all sea squares are connected to each other through other sea squares orthogonally,
2. no two land squares are adjacent orthogonally and
3. 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