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ConcatenatedWords.java
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ConcatenatedWords.java
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package Leetcode;
import java.util.*;
/**
* @author kalpak
*
* 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 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 <= 10^4
* 0 <= words[i].length <= 1000
* words[i] consists of only lowercase English letters.
* 0 <= sum(words[i].length) <= 6 * 10^5
*
*/
public class ConcatenatedWords {
public static List<String> findAllConcatenatedWordsInADict(String[] words) {
List<String> result = new ArrayList<>();
Set<String> wordDict = new HashSet<>(); // List of shorter words
Arrays.sort(words, (a, b) -> (a.length() - b.length()));
for(int i = 0; i< words.length; i++){
if(checkWordBreak(new HashMap<>(), words[i], wordDict))
result.add(words[i]);
wordDict.add(words[i]);
}
return result;
}
private static boolean checkWordBreak(Map<String, Boolean> dp, String s, Set<String> wordDict) {
if(wordDict.isEmpty())
return false;
// Check in dictionary
if(wordDict.contains(s))
return true;
// Check if the string s is already computed
if(dp.containsKey(s))
return dp.get(s);
// recursively check for each substring
for(int i = 1; i <= s.length(); i++) {
String leftWord = s.substring(0, i);
if(wordDict.contains(leftWord) && checkWordBreak(dp, s.substring(i), wordDict)) {
dp.put(s, true);
return true;
}
}
dp.put(s, false);
return false;
}
public static void main(String[] args) {
String[] words = new String[]{"cat","cats","catsdogcats","dog","dogcatsdog","hippopotamuses","rat","ratcatdogcat"};
System.out.println(findAllConcatenatedWordsInADict(words));
}
}