101 lines
2.4 KiB
C
101 lines
2.4 KiB
C
#include <stdio.h>
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#include <stdbool.h>
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#define N 9
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// printf function
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void printBoard(int board[N][N]) {
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for (int i = 0; i < N; i++) {
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for (int j = 0; j < N; j++) {
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printf("%d ", board[i][j]);
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}
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printf("\n");
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}
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}
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// if placing num at board[row][col] is valid
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bool isValid(int board[N][N], int row, int col, int num) {
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// Check row
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for (int x = 0; x < N; x++)
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if (board[row][x] == num)
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return false;
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// Check column
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for (int x = 0; x < N; x++)
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if (board[x][col] == num)
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return false;
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// Check grid
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int startRow = row - row % 3;
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int startCol = col - col % 3;
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for (int i = 0; i < 3; i++)
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for (int j = 0; j < 3; j++)
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if (board[i + startRow][j + startCol] == num)
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return false;
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return true;
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}
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// solve Sudoku using backtracking
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bool solveSudoku(int board[N][N]) {
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int row, col;
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bool emptyFound = false;
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// Find the next empty cell
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for (row = 0; row < N; row++) {
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for (col = 0; col < N; col++) {
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if (board[row][col] == 0) {
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emptyFound = true;
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break;
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}
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}
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if (emptyFound)
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break;
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}
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// No empty cell left, puzzle solved
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if (!emptyFound)
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return true;
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// Try placing digits 1-9
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for (int num = 1; num <= N; num++) {
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if (isValid(board, row, col, num)) {
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board[row][col] = num;
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if (solveSudoku(board))
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return true;
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// Undo if not valid
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board[row][col] = 0;
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}
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}
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return false; // No sol found
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}
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int main() {
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int board[N][N];
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// enter the board values
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printf("Enter the Sudoku board values (use 0 for empty cells):\n");
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for (int i = 0; i < N; i++) {
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for (int j = 0; j < N; j++) {
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printf("Enter value for cell [%d][%d]: ", i + 1, j + 1);
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scanf("%d", &board[i][j]);
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// error handling included
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if (board[i][j] < 0 || board[i][j] > 9) {
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printf("Invalid input. Please enter a number between 0 and 9.\n");
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j--; // Retry current cell
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}
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}
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}
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if (solveSudoku(board)) {
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printf("\nSolved Sudoku:\n");
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printBoard(board);
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} else {
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printf("No solution exists\n");
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}
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return 0;
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}
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