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"

按照题意，基本上能够马上知道这题需要用trie

 class Solution {
     public String replaceWords(List<String> dict, String sentence) {
         String[] tokens = sentence.split(" ");
         TrieNode trie = buildTrie(dict);
         return replaceWords(tokens, trie);
     }

     private String replaceWords(String[] tokens, TrieNode root) {
         StringBuilder stringBuilder = new StringBuilder();
         for (String token : tokens) {
             stringBuilder.append(getShortestReplacement(token, root));
             stringBuilder.append(" ");
         }
         return stringBuilder.substring(, stringBuilder.length()-);
     }

     private String getShortestReplacement(String token, final TrieNode root) {
         TrieNode temp = root;
         StringBuilder stringBuilder = new StringBuilder();
         for (char c : token.toCharArray()) {
             stringBuilder.append(c);
             if (temp.map.containsKey(c)) {
                 if (temp.map.get(c).isWord) {
                     return stringBuilder.toString();
                 }
                 temp = temp.map.get(c);
             } else {
                 return token;
             }
         }
         return token;
     }

     private TrieNode buildTrie(List<String> dict) {
         TrieNode root = new TrieNode(' ');
         for (String word : dict) {
             TrieNode current = root;
             for (char ch : word.toCharArray()) {
                 TrieNode node = current.getChildNode(ch);
                 if (node == null) {
                     current.map.put(ch, new TrieNode(ch));
                     node = current.getChildNode(ch);
                 }
                 current = node;
             }
             current.isWord = true;
         }
         return root;
     }
 }

 class TrieNode {
     char ch;
     boolean isWord;
     Map<Character, TrieNode> map;

     public TrieNode(char ch) {
         this.ch = ch;
         map = new HashMap<>();
     }

     public TrieNode getChildNode(char ch) {
         return map.get(ch);
     }
 }