isValidSudoku.js

// Valid Sudoku
// You are given a a 9 x 9 Sudoku board board. A Sudoku board is valid if the following rules are followed:

// Each row must contain the digits 1-9 without duplicates.
// Each column must contain the digits 1-9 without duplicates.
// Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without duplicates.
// Return true if the Sudoku board is valid, otherwise return false

// Note: A board does not need to be full or be solvable to be valid.
class Solution {
    /**
     * @param {character[][]} board
     * @return {boolean}
     */
    isValidSudoku(board) {
        const cols = new Map();
        const rows = new Map();
        const squares = new Map(); // key = (r / 3) * 3 + c / 3

        for (let r = 0; r < 9; r++) {
            for (let c = 0; c < 9; c++) {
                const cell = board[r][c];
                if (cell === '.') {
                    continue;
                }
                if (
                    rows.get(r)?.has(cell) ||
                    cols.get(c)?.has(cell) ||
                    squares
                        .get(Math.floor(r / 3) * 3 + Math.floor(c / 3))
                        ?.has(cell)
                ) {
                    return false;
                }
                cols.set(c, new Set(cols.get(c)).add(cell));
                rows.set(r, new Set(rows.get(r)).add(cell));
                squares.set(
                    Math.floor(r / 3) * 3 + Math.floor(c / 3),
                    new Set(
                        squares.get(Math.floor(r / 3) * 3 + Math.floor(c / 3)),
                    ).add(cell),
                );
            }
        }
        return true;
    }
}


const solution = new Solution();

// Example 1
let board1 = 
[["1","2",".",".","3",".",".",".","."],
 ["4",".",".","5",".",".",".",".","."],
 [".","9","8",".",".",".",".",".","3"],
 ["5",".",".",".","6",".",".",".","4"],
 [".",".",".","8",".","3",".",".","5"],
 ["7",".",".",".","2",".",".",".","6"],
 [".",".",".",".",".",".","2",".","."],
 [".",".",".","4","1","9",".",".","8"],
 [".",".",".",".","8",".",".","7","9"]]; // true

let board2 = 
[["1","2",".",".","3",".",".",".","."],
 ["4",".",".","5",".",".",".",".","."],
 [".","9","1",".",".",".",".",".","3"],
 ["5",".",".",".","6",".",".",".","4"],
 [".",".",".","8",".","3",".",".","5"],
 ["7",".",".",".","2",".",".",".","6"],
 [".",".",".",".",".",".","2",".","."],
 [".",".",".","4","1","9",".",".","8"],
 [".",".",".",".","8",".",".","7","9"]]; // False

console.log(solution.isValidSudoku(board1));