Mirrored from Sudopedia, the Free Sudoku Reference Guide
Wikipedia article: Ariadne's thread
In the Greek myth of Theseus and the Minotaur, Ariadne gave the hero Theseus a ball of string and advised him to pay out the string behind him as he traversed the maze of the Labyrinth. He could then follow the string back to retrace his path and get out of the maze.
Ariadne's Thread is the name used for a method to solve a complex problem, such as a Sudoku puzzle, by exploring possible alternatives, backtracking when an error is encountered. The process ends when either no more alternatives are available, or when a valid solution is found.
Another name for this technique is Guessing with Backtrack. As with all solving techniques that involve making arbitrary conjectures without the aid of logic, Ariadne's Thread is controversial and typically is employed only when other solving techniques fail to advance the puzzle.
Here is a detailed step-by-step procedure for solving a Sudoku with pencil and paper solely using Ariadne's Thread:
Obviously by itself this is a very tedious and time consuming procedure more suitable for a computer program than for humans. But combined with other solving strategies, it can be a useful last resort. At step 2, repeatedly employ your other solving strategies until you are stuck before proceeding with Ariadne's Thread. Note that if you are working on one of the copied Sudokus, the solving strategies may result in a contradiction or unsolvable situation. In that case, go to step 6 and proceed from there.This page was last modified 17:18, 25 July 2010.