LeetCode in TypeScript

36. Valid Sudoku

Medium

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

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

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.

Example 1:

Input:

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"]]

Output: true

Example 2:

Input:

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"]]

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.

Constraints:

• board.length == 9
• board[i].length == 9
• board[i][j] is a digit 1-9 or '.'.

Solution

function isValidSudoku(board: string[][]): boolean {
    let rowSet: number[] = new Array(9).fill(0)
    let colSet: number[] = new Array(9).fill(0)
    let boxSet: number[] = new Array(9).fill(0)

    for (let i = 0; i < 9; i++) {
        for (let j = 0; j < 9; j++) {
            if (board[i][j] === '.') {
                continue
            }
            let val = board[i][j].charCodeAt(0) - '0'.charCodeAt(0)
            let boxIndex = Math.floor(i / 3) * 3 + Math.floor(j / 3)

            if (rowSet[i] & (1 << val) || colSet[j] & (1 << val) || boxSet[boxIndex] & (1 << val)) {
                return false
            }

            rowSet[i] |= 1 << val
            colSet[j] |= 1 << val
            boxSet[boxIndex] |= 1 << val
        }
    }
    return true
}

export { isValidSudoku }

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