from functools import reduce


def string_to_char(l):
    """Convert 1-D list of strings to 2-D list of chars."""

    if not l:
        return []

    if l == ['']:
        l = [' ']


    maxlen = reduce(max, list(map(len, l)))
    ll = [x.ljust(maxlen) for x in l]
    result = []
    for s in ll:
        result.append([x for x in s])
    return result