class Solution(object):
    def isValidSudoku(self, a):
        rows = [set() for _ in range(9)]
        cols = [set() for _ in range(9)]
        grids = [set() for _ in range(9)]

        for i in range(9):
            for j in range(9):
                if a[i][j] == '.': continue
                g_no = ((i//3) * 3) + j//3
                if a[i][j] in rows[i] or a[i][j] in cols[j] or a[i][j] in grids[g_no]: return False
                rows[i].add(a[i][j])
                cols[j].add(a[i][j])
                grids[g_no].add(a[i][j])
        return True