def find_empty_location(arr, l):
    for row in range(9):
        for col in range(9):
            if arr[row][col] == 0:
                l[0] = row
                l[1] = col
                return True
    return False
def used_in_row(arr, row, num):
    for i in range(9):
        if arr[row][i] == num:
            return True
    return False
def used_in_col(arr, col, num):
    for i in range(9):
        if arr[i][col] == num:
            return True
    return False
def used_in_box(arr, row, col, num):
    for i in range(row // 3 * 3, row // 3 * 3 + 3):
        for j in range(col // 3 * 3, col // 3 * 3 + 3):
            if arr[i][j] == num:
                return True
    return False
def check_location_is_safe(arr, row, col, num):
    return not used_in_row(arr, row, num) and not used_in_col(arr, col, num) and not used_in_box(arr, row, col, num)
def solve_sudoku(arr):
    l = [0, 0]
    if not find_empty_location(arr, l):
        return True
    row = l[0]
    col = l[1]
    for num in range(1, 10):
        if check_location_is_safe(arr, row, col, num):
            arr[row][col] = num
            if solve_sudoku(arr):
                return True
            arr[row][col] = 0
    return False
# 示例数独谜题
grid = [[3, 0, 6, 5, 0, 8, 4, 0, 0],
        [5, 2, 0, 0, 0, 0, 0, 0, 0],
        [0, 8, 7, 0, 0, 0, 0, 3, 1],
        [0, 0, 3, 0, 1, 0, 0, 8, 0],
        [9, 0, 0, 8, 6, 3, 0, 0, 5],
        [0, 5, 0, 0, 9, 0, 6, 0, 0],
        [1, 3, 0, 0, 0, 0, 2, 5, 0],
        [0, 0, 0, 0, 0, 0, 0, 7, 4],
        [0, 0, 5, 2, 0, 6, 3, 0, 0]]

if solve_sudoku(grid):
    for i in range(9):
        for j in range(9):
            print(grid[i][j], end=' ')
        print()
else:
    print("No solution exists")