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36. 有效的数独 #200

Open wengzc opened 3 years ago

wengzc commented 3 years ago

判断一个 9x9 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。

上图是一个部分填充的有效的数独。

数独部分空格内已填入了数字,空白格用 '.' 表示。

示例 1:

输入:
[
  ["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:
[
  ["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。

说明:

题目链接:https://leetcode-cn.com/problems/valid-sudoku

wengzc commented 3 years ago

思路分析:直接拿 37. 解数独 的 isValid 函数遍历二维数组 board 进行判断

/**
 * @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] !== '.') {
                if (!isValid(board, i, j, board[i][j])) return false
            }
        }
    }
    return true
    // 判断 board[i][j] 是否有效
    function isValid(board, row, column, c) {
        for (let i = 0; i < 9; i++) {
            // 判断行是否重复
            if (column !== i && board[row][i] === c) return false
            // 判断列是否重复
            if (row !== i && board[i][column] === c) return false
            // 判断 3 x 3 方框是否存在重复
            let m = Math.floor(row / 3) * 3 + Math.floor(i / 3)
            let n = Math.floor(column / 3) * 3 + i % 3
            if (m !== row && n !== column && board[m][n] === c) return false
        }
        return true
    }
};