def wordBreak(self, s, wordDict):
    queue = [0]
    dictionary_set = set(wordDict)
    for left in queue:
        for right in range(left,len(s)):
            if s[left:right+1] in dictionary_set:
                if right == len(s)-1:
                    return True
                queue.append(right+1)
    return False

s = 'aab'
wordDict = ['a','aa','aaa']