12/15/2023 0 Comments Sudoku 9x9 easy swing javaThis process continues until it finds correct solution or reach to the stage from where no solution can be found.ĭisplaySudoku() method is used to display 9×9 array in form of sudoku. ![]() But in case no other possible number remains, again it will bactrack to previously assigned cell and process continues. If it finds any allowed number, then it assigns this new number to cell and process continues again. If function returns false, control will backtrack to previously assigned cell and try for another number there. This process continues until it finds some cell for which no number is allowed and function will return false. It checks for allowed numbers from 1 to 9, assign the first possible option to cell and again call solveSudoku() method for next UNASSIGNED cell. It checks cells in each row one by one and picks up first cell with UNASSIGNED value. SolveSudoku() method starts traversing from top left cell to the right side. Return !(containsInRow(row, number) || containsInCol(col, number) || containsInBox(row, col, number)) Private boolean isAllowed(int row, int col,int number) If any of above three method return true, it means particular number is not allowed in that cell. IsAllowed() method uses above three methods to check if it is safe to assign number in the cell. ![]() Private boolean containsInBox(int row, int col,int number) Private boolean containsInCol(int col,int number) Private boolean containsInRow(int row,int number) private boolean containsInRow(int row,int number)īelow three methods are used to check, if number is present in current row, current column and current 3X3 subgrid or not. 0 value in any of its cell, is considered to be incomplete or wrong. Instance variable sudoku can be initialized using any of the below two constructors.Īll the cells of completely solved sudoku array must have assigned valid values. Sudoku, 9×9 int array is used to store all the elements of sudoku. Approach for solving sudoku using recursive backtracking algorithm Backtracking is also known as depth-first search. But backtrack to where? to the previous choice point. Think of a labyrinth or maze – how do you find a way from an entrance to an exit? Once you reach a dead end, you must backtrack. Briefly, once you exhaust all your options at a certain step you go back. If at some step it becomes clear that the current path that you are on cannot lead to a solution you go back to the previous step (backtrack) and choose a different path. In backtracking algorithms you try to build a solution one step at a time. Sudoku can be solved using recursive backtracking algorithm. For other Backtracking algorithms, check my posts under section Backtracking (Recursion). If you are interested in java programs for other board games like Sudoku Checker, Tic Tac Toe, Snake N Lader and N Queen Problem , you can check out my posts in Board Games section. If you are looking for program to check correctness of Sudoku, you will find it in my post Sudoku checker (By traversing each cell only once). This might help to focus on certain areas of the grid.This post is about generating solution for sudoku problem and not for checking if solution is correct or not. Look for Grid Symmetry: Often, the given numbers (and therefore the solution) have a symmetrical arrangement.Double Pairs: If two cells in a row, column, or region can only be two numbers (like 3 and 6), then eliminate these two numbers from the other cells in that section.Elimination: Determine what numbers cannot be in a cell to figure out what number can be.Single Possibility: If a cell is the only one in its row, column, or region that can contain a particular number, that number must go in that cell.Unique Asterisk Numbers: The numbers 1 through 9 must appear without repetition in the shaded asterisk area, in addition to the standard Sudoku rules.Asterisk Region: There is an additional, specially shaded area (forming an asterisk shape) in the grid.Number Placement: The player must fill the empty cells with numbers 1 through 9.Givens: Some cells are pre-filled with numbers, known as "givens.".Grid Structure: The puzzle consists of a 9x9 grid, and this grid is further divided into 3x3 subgrids/regions.In the Asterisk Sudoku variant, an additional constraint is introduced with a specially shaded area, an "asterisk," which must also contain the numbers 1 through 9 without repetition. Asterisk Sudoku is a variant of the classic Sudoku, a number placement puzzle traditionally presented in a 9x9 grid, subdivided into 3x3 subgrids or "regions." The grid partially fills with numbers, referred to as "givens." The objective is to populate the empty cells in such a way that each number 1 through 9 appears exactly once in each row, column, and region.
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