A Sudoku solver is a computer program that can solve Sudoku puzzles automatically. Sudoku is a logic-based number puzzle that requires the player to fill in a 9x9 grid with numbers 1 through 9, ensuring that each row, column, and 3x3 sub-grid contains all the numbers from 1 through 9 without repetition. A Sudoku solver typically takes a partially filled-in puzzle as input and outputs a complete solution, or confirms that there is no solution if the puzzle is invalid.

Sudoku solvers use a combination of techniques to solve puzzles. The simplest approach is brute force, where the solver tries all possible combinations of numbers until it finds a solution. However, this approach is computationally expensive and not practical for solving large puzzles.

More efficient Sudoku solvers use a combination of logic and deduction to eliminate possibilities and narrow down the solution space. Techniques such as naked pairs, hidden pairs, X-Wings, and Swordfish are commonly used to eliminate possibilities and make progress towards a solution. These techniques involve looking for patterns of numbers in rows, columns, and sub-grids to eliminate possibilities and find the correct solution.

Sudoku solvers are often implemented as computer programs in various programming languages. Some solvers are standalone applications that can be run on a computer or mobile device, while others are integrated into websites or mobile apps that allow users to enter a Sudoku puzzle and get a solution in real time. Sudoku solvers are useful tools for people who enjoy playing Sudoku and want to check their solutions or get help solving a challenging puzzle.
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