36. 有效的数独 #

原题链接：LeetCode 36. 有效的数独

题目描述 #

请你判断一个 9 x 9 的数独是否有效。只需要** 根据以下规则** ，验证已经填入的数字是否有效即可。

• 数字 1-9 在每一行只能出现一次。

• 数字 1-9 在每一列只能出现一次。

• 数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。（请参考示例图）

注意：

• 一个有效的数独（部分已被填充）不一定是可解的。

• 只需要根据以上规则，验证已经填入的数字是否有效即可。

• 空白格用 '.' 表示。

示例 1：

• 输入： board = [["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"]]
• 输出： true

示例 2：

• 输入： board = [["8","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"]]
• 输出： false
• 解释： 除了第一行的第一个数字从** 5** 改为 **8 **以外，空格内其他数字均与 示例1 相同。 但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。

提示：

• board.length == 9

• ``board[i].length == 9

• board[i][j]`` 是一位数字（1-9）或者 '.'

难度： Medium

题解代码 #

/**
 * @param {character[][]} board
 * @return {boolean}
 */
 var isValidSudoku = function(board) {
  for (let i = 0; i < 9; i++) {
    for (let j = 0; j < 9; j++) {
      if (board[i][j] === '.') continue
      // 替换当前值
      const temp = board[i][j]
      board[i][j] = '.'
      if (!isValid(board, i, j, temp)) return false
      board[i][j] = temp
    }
  }
  return true
};

function isValid (board, row, col, k) {
  const x = Math.floor(row / 3) * 3
  const y = Math.floor(col / 3) * 3
  // 9x9
  for (let i = 0; i < 9; i++) {
    if (board[row][i] === k || board[i][col] === k) return false
  }
  // 3x3
  for (let i = 0; i < 3; i++) {
    for (let j = 0; j < 3; j++) {
      if (board[x + i][y + j] === k) return false
    }
  }
  return true
}