Leet Code 648. Replace Words

Example 1:
Input: dictionary = ["cat","bat","rat"], sentence = "the cattle was rattled by the battery"
Output: "the cat was rat by the bat"

package pep.Day80;

import java.util.LinkedList;
import java.util.List;

public class LeetCode_648_Replcae_Words {
    public static void main(String[] args) {
        List<String> dictionary = new LinkedList<>();
        dictionary.add("cat");
        dictionary.add("bat");
        dictionary.add("rat");
        String sentence = "the cattle was rattled by the battery";
        System.out.println(replaceWords(dictionary, sentence));
    }

    static class Node {
        Node[] children = new Node[26];
        String isEnd = null;
    }

    static Node root = new Node();

    public static void insert(String word) {
        Node curr = root;
        for (int i = 0; i < word.length(); i++) {
            char tba = word.charAt(i);
            if (curr.children[tba - 'a'] == null)
                curr.children[tba - 'a'] = new Node();
            curr = curr.children[tba - 'a'];
        }
        curr.isEnd = word;
    }

    public static String replaceWords(List<String> dictionary, String sentence) {

        // dictionary ke sare word TRIES me daal do
        for (String word : dictionary) {
            insert(word);
        }

        StringBuilder sb = new StringBuilder();
        // sentence ke har word pr jaate hain aur prefix mngwate hain
        for (String word : sentence.split(" ")) {
            String prefix = getPrefix(word);

            if (prefix != null) {
                sb.append(prefix);
            } else {
                sb.append(word);
            }
            sb.append(" ");
        }

        return sb.toString().substring(0, sb.length() - 1);


    }

    private static String getPrefix(String word) {
        Node curr = root;
        for (int i = 0; i < word.length(); i++) {
            char tbf = word.charAt(i);
            if (curr.children[tbf - 'a'] == null) {
                return null;
            }

            if (curr.children[tbf - 'a'].isEnd != null) {
                return curr.children[tbf - 'a'].isEnd;
            } else {
                curr = curr.children[tbf - 'a'];
            }

        }
        return null;
    }
}