给出一个字符串S。该字符串只有小写英文字母。您必须将字符串分成尽可能多的连续子字符串，以使S中的每个字母仅出现在一个子字符串中，这些子字符串的串联产生S。
S = "abcde"
"ab", "cd", "e"
"a", "b", "c", "d", "e" -> Answer
S = "abcae"
"a", "b", "c", "a", "e" -> Wrong
"abc", "a", "e" -> Wrong
"abca", "e" -> Meets constraint (Answer)
"abcae" -> Meets constratint but is not maximal(Not the answer)
S = "abcabe"
"abcab", "e" -> Meets constratint + maximal (Answer)
"abca", "b", "e" -> Wrong because 'b' appears in multiple substrings.