/** Hello guys My first code in C This is sudoku solver Enter the desired sudoku and enter 0 for unknown value For example: 0 0 0 1 2 3 0 0 4 0 0 2 4 5 0 0 0 0 1 0 0 0 0 0 6 7 8 ................ like this this is 9×9 sudoku **/ #include int sudoku[9][9]; //The array which stores entries for the sudoku void solvesudoku(int, int); int checkrow(int row, int num) { //This function checks whether we can put the number(num) in the row(row) of the Sudoku or not int column; for (column = 0; column < 9; column++) { if (sudoku[row][column] == num) { //If the number is found already present at certain location we return zero return 0; } } //If the number is not found anywhere we return 1 return 1; } int checkcolumn(int column, int num) { //This function checks whether we can put the number(num) in the column(column) of the Sudoku or not int row; for (row = 0; row < 9; row++) { if (sudoku[row][column] == num) { //If the number is found already present at certain location we return zero return 0; } } //If the number is not found anywhere we return 1 return 1; } int checkgrid(int row, int column, int num) { //This function checks whether we can put the number(num) in the 3*3 grid or not //We get the starting row and column for the 3*3 grid row = (row / 3) * 3; column = (column / 3) * 3; int r, c; for (r = 0; r < 3; r++) { for (c = 0; c < 3; c++) { if (sudoku[row + r][column + c] == num) { //If the number is found already present at certain location we return zero return 0; } } } //If the number is not found anywhere we return 1 return 1; } void navigate(int row, int column) { //Function to move to the next cell in case we have filled one cell if (column < 8) solvesudoku(row, column + 1); else solvesudoku(row + 1, 0); } void display() { //The function to display the solved Sudoku int row, column; printf("THE SOLVED SUDOKU \n"); for (row = 0; row < 9; row++) { for (column = 0; column < 9; column++) printf("%d ", sudoku[row][column]); printf("\n"); } } void solvesudoku(int row, int column) { //If the row number is greater than 8 than we have filled all cells hence we have solved the sudoku if (row > 8) display(); if (sudoku[row][column] != 0) { //If the value filled at a cell is not zero than it is filled with some value from 0 to 9 hence we move further navigate(row, column); } else { //This is a counter to check numbers from 1 to 9 whether the number can be filled in the cell or not int ctr; for (ctr = 1; ctr <= 9; ctr++) { //We check row,column and the grid if ((checkrow(row, ctr) == 1) && (checkcolumn(column, ctr) == 1) && (checkgrid(row, column, ctr) == 1)) { sudoku[row][column] = ctr; navigate(row, column); } } //No valid number was found so we clean up and return to the caller. sudoku[row][column] = 0; } } int main() { int row, column; printf("Enter the desired sudoku and enter 0 for unknown entries\n"); for (row = 0; row < 9; row++) for (column = 0; column < 9; column++) scanf("%d", &sudoku[row][column]); //We start solving the sudoku. solvesudoku(0, 0); return 0; }

SUDOKU SOLVER