The World's Hardest Sudoku
I went camping recently and got in an argument with a friend who’s more like a sister — in that I’d rather gouge my eyes out than admit she’s right. We were making mere small talk about Sudoku, as one does. I said something like “but yeah, some get so hard you have to guess.” That triggered a nuclear war.
Her claim: you never need to guess. My claim: some puzzles are so hard you have to try a value in a cell and see if it leads to a contradiction.
So I did what any well adjusted person would do. Forget about it and move on? NOPE
AI Everest
Arto Inkala, 2012 · 21 clues
Every standard technique, run against the opening position:
Illustration only — just the cells that matter.
Nothing. Not one digit, not one eliminated candidate. This is where most people put the pencil down. Tap any technique to see what it looks for.
Fifteen proofs by contradiction before a single digit can be written down. I printed it out at the office and 4 people spent 30 minutes trying to get a single square, but no one could.
I dedicate this page to everyone out there who was told they were wrong, and I hope my pettiness inspires you to prioritize the truth over your friendships. Friends die. Truth is eternal.