AI SUDOKU
The Sudoku Blog
The Sudoku Blog covers the ideas behind the game — how a solver generates a puzzle that has exactly one answer, and the human logic techniques that the AI Hint engine uses to solve it.
How a Sudoku Solver Works: Backtracking and Unique Solutions
Depth-first search, constraint checking, and the clever uniqueness test that guarantees every generated puzzle has exactly one solution — so you never have to guess.
Read StrategyThe Logic Techniques Behind Every Sudoku
From naked and hidden singles up to pairs, pointing pairs and the X-Wing — the deductions that turn a wall of empty cells into a fully solved grid.
Read HistoryThe History of Sudoku — From Latin Squares to a Global Craze
From Euler's Latin squares to Howard Garns' 1979 "Number Place," Nikoli naming it in Japan, and Wayne Gould's 2004 boom in The Times — how the puzzle conquered the world.
ReadThe three posts split cleanly into how the puzzle is built, how it is solved by hand, and where it came from. The solver post explains the backtracking algorithm that both generates and verifies every puzzle on this site, and why checking for a unique solution is what separates a fair Sudoku from a guessing game. The techniques post walks through the same ladder of logic the AI Hint engine climbs, from a lone candidate in a single cell up to multi-cell patterns like the X-Wing. The history post traces the puzzle back past its Japanese name to Leonhard Euler's 18th-century Latin squares, through its 1979 American debut as Number Place, and on to the 2004 newspaper boom that made it a household game worldwide.