input: Write a function to solve a Sudoku puzzle given a 9x9 board. The function should return True if a solution exists and modify the board to reflect the solution, or return False if no solution exists.
  assert solve_sudoku([
      [7,8,0,4,0,0,1,2,0],
      [6,0,0,0,7,5,0,0,9],
      [0,0,0,6,0,1,0,7,8],
      [0,0,7,0,4,0,2,6,0],
      [0,0,1,0,5,0,9,3,0],
      [9,0,4,0,6,0,0,0,5],
      [0,7,0,3,0,0,0,1,2],
      [1,2,0,0,0,7,4,0,0],
      [0,4,9,2,0,6,0,0,7]
  ])==True
  assert solve_sudoku([
      [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]
  ])==True
  assert solve_sudoku([
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0],
      [0,0,0,0,0,0,0,0,0]
  ])==True
  assert solve_sudoku([
      [0,0,0,0,0,0,0,0,1],
      [0,0,0,0,1,0,0,0,0],
      [0,0,1,0,0,0,0,0,0],
      [0,0,0,1,0,0,0,0,0],
      [0,0,0,0,0,1,0,0,0],
      [0,0,0,0,0,0,1,0,0],
      [0,0,0,0,0,0,0,1,0],
      [1,0,0,0,0,0,0,0,0],
      [0,1,0,0,0,0,0,0,0]
  ])==False
  assert solve_sudoku([])==False
output: def solve_sudoku(board):
      def is_valid(board, row, col, num):
          for i in range(9):
              if board[row][i] == num or board[i][col] == num or board[row//3*3 + i//3][col//3*3 + i%3] == num:
                  return False
          return True
  
      def solve(board):
          for row in range(9):
              for col in range(9):
                  if board[row][col] == 0:
                      for num in range(1, 10):
                          if is_valid(board, row, col, num):
                              board[row][col] = num
                              if solve(board):
                                  return True
                              board[row][col] = 0
                      return False
          return True
  
      if len(board) != 9 or any(len(row) != 9 for row in board):
          return False
      return solve(board)