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

#define SIZE 9

void printSudoku(int board[SIZE][SIZE]) {
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++) {
            if (j % 3 == 0 && j != 0) {
                printf("| ");
            }
            printf("%d ", board[i][j] == 0 ? '.' : board[i][j]);
        }
        printf("\n");
        if ((i + 1) % 3 == 0 && i != 8) {
            printf("---------------------\n");
        }
    }
}

bool isValidPlacement(int board[SIZE][SIZE], int row_check[SIZE][SIZE], int col_check[SIZE][SIZE],
    int block_check[SIZE][SIZE], int num, int row, int col) {
    int blockIndex = (row / 3) * 3 + (col / 3);
    if (row_check[row][num - 1] || col_check[col][num - 1] || block_check[blockIndex][num - 1]) {
        return false; // 数字已在行、列或3x3块中存在
    }
    return true;
}

void setPlacement(int row_check[SIZE][SIZE], int col_check[SIZE][SIZE],
    int block_check[SIZE][SIZE], int num, int row, int col, bool placed) {
    int blockIndex = (row / 3) * 3 + (col / 3);
    row_check[row][num - 1] = placed;
    col_check[col][num - 1] = placed;
    block_check[blockIndex][num - 1] = placed;
}

bool isValidSudoku(int board[SIZE][SIZE]) {
    int row_check[SIZE][SIZE] = { 0 };
    int col_check[SIZE][SIZE] = { 0 };
    int block_check[SIZE][SIZE] = { 0 };

    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++) {
            int num = board[i][j];
            if (num != 0) {
                if (!isValidPlacement(board, row_check, col_check, block_check, num, i, j)) {
                    printf("False: Invalid initial Sudoku matrix!\n");
                    printf("The number %d has conflicts!\n", num);
                    return false;
                }
                setPlacement(row_check, col_check, block_check, num, i, j, true);
            }
        }
    }
    return true;
}

bool solveSudoku(int board[SIZE][SIZE]) {
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++) {
            if (board[i][j] == 0) { // 找到一个空的位置
                for (int num = 1; num <= 9; num++) {
                    board[i][j] = num; // 填入数字

                    if (isValidSudoku(board)) {
                        if (solveSudoku(board)) {
                            return true; // 若成功，则返回
                        }
                    }
                    board[i][j] = 0; // 撤销填入，重试下一个数字
                }
                return false; // 若所有数字尝试均不行，则返回不成功
            }
        }
    }
    return true; // 全部填满，返回成功
}

int main() {
    int board0[SIZE][SIZE] = {
        {5, 3, 0, 0, 7, 0, 0, 0, 0},
        {6, 0, 0, 1, 9, 5, 0, 0, 0},
        {0, 9, 8, 0, 0, 0, 0, 6, 0},
        {8, 0, 0, 0, 6, 0, 0, 0, 3},
        {4, 0, 0, 8, 0, 3, 0, 0, 1},
        {7, 0, 0, 0, 2, 0, 0, 0, 6},
        {0, 6, 0, 0, 0, 0, 2, 8, 0},
        {0, 0, 0, 4, 1, 9, 0, 0, 5},
        {0, 0, 0, 0, 8, 0, 0, 7, 9}
    };

    int board1[SIZE][SIZE] = {
        {8, 3, 0, 0, 7, 0, 0, 0, 0},
        {6, 0, 0, 1, 9, 5, 0, 0, 0},
        {0, 9, 8, 0, 0, 0, 0, 6, 0},
        {8, 0, 0, 0, 6, 0, 0, 0, 3},
        {4, 0, 0, 8, 0, 3, 0, 0, 1},
        {7, 0, 0, 0, 2, 0, 0, 0, 6},
        {0, 6, 0, 0, 0, 0, 2, 8, 0},
        {0, 0, 0, 4, 1, 9, 0, 0, 5},
        {0, 0, 0, 0, 8, 0, 0, 7, 9}
    };

    for (int boardIndex = 0; boardIndex < 2; boardIndex++) {
        int (*currentBoard)[SIZE] = boardIndex == 0 ? board0 : board1;

        printf("The original Sudoku matrix:\n");
        printSudoku(currentBoard);
        if (isValidSudoku(currentBoard)) {
            printf("True: Valid initial Sudoku matrix!\n");
            if (solveSudoku(currentBoard)) {
                printf("The solution of Sudoku matrix:\n");
                printSudoku(currentBoard);
            }
            else {
                printf("No solution!\n");
            }
        }
        else {
            printf("False: Invalid initial Sudoku matrix!\n");
            printf("No solution!\n");
        }
        printf("\n");
    }

    return 0;
}