def split(s):

    i = 0

    ans = []

    while i < len(s):

        start = i

        # find space

        while i < len(s) and s[i] != ' ':

            i += 1

        ans.append(s[start:i])

        i += 1

    if s and s[-1] == " ":

        ans.append("")

    return ans

assert split("") == []

assert split(" ") == ["", ""]

assert split("  ") == ["", "", ""]

assert split("a") == ["a"]

assert split("a b") == ["a", "b"]

assert split(" a") == ["", "a"]

assert split("a ") == ["a", ""]

assert split(" a b") == ["", "a", "b"]

assert split("a b ") == ["a", "b", ""]

assert split("ac bcd") == ["ac", "bcd"]