【python3】leetcode 648. Replace Words (Medium)

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648. Replace Words (Medium) 

In English, we have a concept called root, which can be followed by some other words to form another longer word - let's call this word successor. For example, the root an, followed by other, which can form another word another.

Now, given a dictionary consisting of many roots and a sentence. You need to replace all the successor in the sentence with the root forming it. If a successor has many roots can form it, replace it with the root with the shortest length.

You need to output the sentence after the replacement.

Example 1:

Input: dict = ["cat", "bat", "rat"]
sentence = "the cattle was rattled by the battery"
Output: "the cat was rat by the bat"

Note:

1. The input will only have lower-case letters.
2. 1 <= dict words number <= 1000
3. 1 <= sentence words number <= 1000
4. 1 <= root length <= 100
5. 1 <= sentence words length <= 1000

要求把带有词根的单词换成词根返回

1 时间复杂度O(n2) not fast（Accepted）

class Solution:
    def replaceWords(self, dict, sentence):
        """
        :type dict: List[str]
        :type sentence: str
        :rtype: str
        """
        words = sentence.split()
        str = []
        for i,w in enumerate(words):
            flag = 0
            for root in dict:
                if root in w and w.index(root) == 0: 
                    flag = 1
                    str.append(root)
                    break
            if flag == 0:str.append(w)   
                
        return " ".join(str)