648. Replace Words (Medium)

https://leetcode.com/problems/replace-words/

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

 

Hints

Solutions

class Solution {
    public String replaceWords(List<String> roots, String sentence) {
        Set<String> rootset = new HashSet();
        for (String root: roots) rootset.add(root);

        StringBuilder ans = new StringBuilder();
        for (String word: sentence.split("\\s+")) {
            String prefix = "";
            for (int i = 1; i <= word.length(); ++i) {
                prefix = word.substring(0, i);
                if (rootset.contains(prefix)) break;
            }
            if (ans.length() > 0) ans.append(" ");
            ans.append(prefix);
        }
        return ans.toString();
    }
}
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