472. Concatenated Words

Problem Link

Description

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Given an array of strings words (without duplicates), return all the concatenated words in the given list of words.

A concatenated word is defined as a string that is comprised entirely of at least two shorter words (not necessarily distinct) in the given array.

 

Example 1:

Input: words = ["cat","cats","catsdogcats","dog","dogcatsdog","hippopotamuses","rat","ratcatdogcat"]
Output: ["catsdogcats","dogcatsdog","ratcatdogcat"]
Explanation: "catsdogcats" can be concatenated by "cats", "dog" and "cats"; 
"dogcatsdog" can be concatenated by "dog", "cats" and "dog"; 
"ratcatdogcat" can be concatenated by "rat", "cat", "dog" and "cat".

Example 2:

Input: words = ["cat","dog","catdog"]
Output: ["catdog"]

 

Constraints:

• 1 <= words.length <= 104
• 1 <= words[i].length <= 30
• words[i] consists of only lowercase English letters.
• All the strings of words are unique.
• 1 <= sum(words[i].length) <= 105

Solution

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Python3

class Solution:
    def findAllConcatenatedWordsInADict(self, words: List[str]) -> List[str]:
        s = set(words)
 
        @cache
        def go(word):
            for i in range(1, len(word)):
                prefix = word[:i]
                suffix = word[i:]
 
                if prefix in s and (suffix in s or go(suffix)):
                    return True
            
            return False
        
        res = []
        for word in words:
            if go(word):
                res.append(word)
        
        return res