05/09/26 tough puzzle from sudoku.com.au
This one is equivalent to 05/09/12. Proof :
1) Take 05/09/12 grid, turn it 90° clockwise.
2) Now move rows 123456789 (1=bottom!) on new positions 213654798, then move columns abcdefghi(a=left!) on new positions ighdefbca. Do you begin to feel like déjà vu?
All that's left now is to renumber last grid's values 123456789 on 137648259 and you get exactly 05/09/26's puzzle.
4) Now applying the same "dictionary" (rotating, changing rows, columns, values) to proof of
09/12 you will mechanically get a proof of today's. Try it !
See equivalent puzzles :
09/12,09/26,09/27,
09/29,
10/02.