text: var isValidSudoku = function(folha) {
      
      const linha = [], coluna = [], bloco = [];
      for(let i = 0; i < folha.length; i++) {
          linha.push(new Set());
          coluna.push(new Set());
          bloco.push(new Set());
      }
      
      for(let i = 0; i < folha.length; i++) {
          for(let j = 0; j < folha[i].length; j++) {
              const cell = folha[i][j];
              if(cell === '.') continue;
              const blocoNum = 3 * Math.floor(i / 3) + Math.floor(j / 3);
              if(linha[i].has(cell) || coluna[j].has(cell) || bloco[blocoNum].has(cell))
                  return false;
              linha[i].add(cell);
              coluna[j].add(cell);
              bloco[blocoNum].add(cell);
          }
      }
      
      return true
      
    };