LeetCode 36. Valid Sudoku

Description

Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

Each row must contain the digits 1-9 without repetition.

Each column must contain the digits 1-9 without repetition.

Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.

A partially filled sudoku which is valid.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

验证数独

Example 1:

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Input:
[
  ["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"]
]
Output: true

Example 2:

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Input:
[
  ["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"]
]
Output: false

Explanation: Same as Example 1, except with the 5 in the top left corner being modified to 8.
Since there are two 8's in the top left 3x3 sub-box, it is invalid.

Note:

A Sudoku board (partially filled) could be valid but is not necessarily solvable.
Only the filled cells need to be validated according to the mentioned rules.
The given board contain only digits 1-9 and the character ‘.’.
The given board size is always 9x9.

判断数独板是否有效。

注：

一个数组板可以是有效但是无解的。

Solution

根据题意只需要判断数独板中给出的数字在行列和3x3格子中是否有重复即可。而不需要判断是否可以解。

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func isValidSudoku(board [][]byte) bool {
    // 用于标记第x列已使用的数字
    colUsed := [9][9]bool{}
    // 用于标记3x3小方格已使用的数字
    subBoxUsed := [3][3][9]bool{}

    for row := 0; row < 9; row++ {
        // 用于标记当前行已使用的数字
        rowUsed := [9]bool{}

        for col := 0; col < 9; col++ {
            b := board[row][col]
            if b == '.' {
                continue
            }

            num := b - '0' - 1

            // 检查数字是否已使用
            if rowUsed[num] || colUsed[col][num] || subBoxUsed[row / 3][col / 3][num] {
                return false
            }

            // 标记为已使用
            rowUsed[num] = true
            colUsed[col][num] = true
            subBoxUsed[row / 3][col / 3][num] = true
        }
    }

    return true
}

LeetCode 36. Valid Sudoku

LeetCode 练习 36. Valid Sudoku - Answer LeetCode编程练习解答

Description

Solution

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