In a 9*9 SUDOKU game
what is the minimal number of digits guaranteeing a unique solution?
The mallest known number of clues a sudoku puzzle can have and still be solvable is 17. Gordon Royle maintains a database of all known puzzles, 48862 so far, but has yet to find a 16 clue puzzle.
http://units.maths.uwa.edu.au/~gordon/sudokumin.php
One such puzzle is below (solvable by hand, with persistance)
...|...|.1.
4..|...|...
.2.|...|...
---+---+---
...|.5.|4.7
..8|...|3..
..1|.9.|...
---+---+---
3..|4..|2..
.5.|1..|...
...|8.6|...
Smallest known number of clues
