Place any one number from 1 to N exactly once in each of the 4N thickly outlined regions. Every row and column must contain either no number, or two instances of the same number. Numbers cannot be placed in shaded cells.
(Rules (modified) and example (N=3) from WPC 2017 IB)
The ruleset is slightly modified from the one in WPC IB. In the original rules, if the number of regions were larger than 4N, it was possible for a number to have non-rectangular formation.
History of the puzzle
Invented by Anurag Sahay (India) in 2017 as a submission for Puzzle Innovations Contest, a pre-event of WPC 2017.
Appearances in the past WPCs
- WPC 2017/Round 18 by Swaroop Guggilam