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Some hobbyists have developed computer programs that will solve Sudoku puzzles using a backtracking algorithm, which is a type of brute force search. [3] Backtracking is a depth-first search (in contrast to a breadth-first search), because it will completely explore one branch to a possible solution before moving to another branch.
The general problem of solving Sudoku puzzles on n 2 ×n 2 grids of n×n blocks is known to be NP-complete. [8] A puzzle can be expressed as a graph coloring problem. [9] The aim is to construct a 9-coloring of a particular graph, given a partial 9-coloring. The Sudoku graph has 81 vertices, one vertex for each cell.
Many Sudoku solving algorithms, such as brute force-backtracking and dancing links can solve most 9×9 puzzles efficiently, but combinatorial explosion occurs as n increases, creating practical limits to the properties of Sudokus that can be constructed, analyzed, and solved as n increases.
Backtracking is an important tool for solving constraint satisfaction problems, [2] such as crosswords, verbal arithmetic, Sudoku, and many other puzzles. It is often the most convenient technique for parsing , [ 3 ] for the knapsack problem and other combinatorial optimization problems.
Tanner graph of a Sudoku. denotes the entries of the Sudoku in row-scan order. denotes the constraint functions: =, …, associated with rows, =, …, associated with columns and =, …, associated with the sub-grids of the Sudoku.. There are several possible decoding methods for sudoku codes. Some algorithms are very specific developments for Sudoku codes. Several methods are described in ...
After an introductory chapter on Sudoku and its deductive puzzle-solving techniques [1] (also touching on Euler tours and Hamiltonian cycles), [5] the book has eight more chapters and an epilogue. Chapters two and three discuss Latin squares , the thirty-six officers problem , Leonhard Euler 's incorrect conjecture on Graeco-Latin squares , and ...
The Dancing Links algorithm solving a polycube puzzle In computer science , dancing links ( DLX ) is a technique for adding and deleting a node from a circular doubly linked list . It is particularly useful for efficiently implementing backtracking algorithms, such as Knuth's Algorithm X for the exact cover problem . [ 1 ]
A final two chapters provide brief hints and more detailed solutions to the puzzles, [2] with the solutions forming the majority of pages of the book. [3] Some of the puzzles are well known classics, some are variations of known puzzles making them more algorithmic, and some are new. [4] They include: