https://leetcode.com/problems/valid-sudoku/submissions/

validSudoku.js

/**
 * @param {character[][]} board
 * @return {boolean}
 */
var isValidSudoku = function(board) {
    
    const allowedChars = new Set('123456789');
    
    const rowSets = new Array(9).fill(0).map(()=> new Set());
    const colSets = new Array(9).fill(0).map(()=> new Set());
    const sqSets = new Array(9).fill(0).map(()=> new Set());
    
    for(let row = 0; row<9; row++){
        for(let col = 0; col<9; col++){
            
            const sq = board[row][col];
            if(sq === '.') continue;
            
            if(!allowedChars.has(sq)) return false;
            
            if(rowSets[row].has(sq)) return false;
            if(colSets[col].has(sq)) return false;
            
            const squareIndex = Math.floor(row/3)*3 + Math.floor(col/3);
            if(sqSets[squareIndex].has(sq)) return false;
            
            rowSets[row].add(sq);
            colSets[col].add(sq);
            sqSets[squareIndex].add(sq);
        }
    }
    
    return true;
};