#include <stdio.h>
#include <stdbool.h>

void print_sudoku(char sudoku[9][9]) {
    for (int i = 0; i < 9; i++) {
        if (i % 3 == 0 && i != 0) {
            printf("-------------------------\n");
        }
        for (int j = 0; j < 9; j++) {
            if (j % 3 == 0 && j != 0) {
                printf("| ");
            }
            printf("%c ", sudoku[i][j]);
        }
        printf("\n");
    }
}

bool is_valid_sudoku(char sudoku[9][9]) {
    // Check rows
    for (int i = 0; i < 9; i++) {
        int seen[9] = { 0 };
        for (int j = 0; j < 9; j++) {
            if (sudoku[i][j] != '.' && seen[sudoku[i][j] - '1'] == 1) {
                printf("False: Invalid initial Sudoku matrix! The number %c in row %d has been used!\n", sudoku[i][j], i + 1);
                return false;
            }
            seen[sudoku[i][j] - '1'] = 1;
        }
    }

    // Check columns
    for (int j = 0; j < 9; j++) {
        int seen[9] = { 0 };
        for (int i = 0; i < 9; i++) {
            if (sudoku[i][j] != '.' && seen[sudoku[i][j] - '1'] == 1) {
                printf("False: Invalid initial Sudoku matrix! The number %c in col %d has been used!\n", sudoku[i][j], j + 1);
                return false;
            }
            seen[sudoku[i][j] - '1'] = 1;
        }
    }

    // Check 3x3 blocks
    for (int block = 0; block < 9; block++) {
        int seen[9] = { 0 };
        for (int i = block / 3 * 3; i < block / 3 * 3 + 3; i++) {
            for (int j = block % 3 * 3; j < block % 3 * 3 + 3; j++) {
                if (sudoku[i][j] != '.' && seen[sudoku[i][j] - '1'] == 1) {
                    printf("False: Invalid initial Sudoku matrix! The number %c in block %d has been used!\n", sudoku[i][j], block + 1);
                    return false;
                }
                seen[sudoku[i][j] - '1'] = 1;
            }
        }
    }

    printf("True: Valid initial Sudoku matrix!\n");
    return true;
}

int main() {
    char sudoku_board[9][9] = {
        {'5', '3', '.', '.', '7', '.', '.', '.', '.'},
        {'6', '.', '.', '1', '9', '5', '.', '.', '.'},
        {'.', '9', '8', '.', '.', '.', '.', '6', '.'},
        {'8', '.', '.', '.', '6', '.', '.', '.', '3'},
        {'4', '.', '.', '8', '.', '3', '.', '.', '1'},
        {'7', '.', '.', '.', '2', '.', '.', '.', '6'},
        {'.', '6', '.', '.', '.', '.', '2', '8', '.'},
        {'.', '.', '.', '4', '1', '9', '.', '.', '5'},
        {'.', '.', '.', '.', '8', '.', '.', '7', '9'}
    };


    printf("The original Sudoku matrix: \n");
    print_sudoku(sudoku_board);

    is_valid_sudoku(sudoku_board);

    return 0;
}