LeetCode--648--medium--ReplaceWords

summary:

 construct trie | traversal 

package com.odyssey.app.algorithm.lc.trie;

import java.util.ArrayList;
import java.util.List;

/**
 * 648
 * 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:
 *
 * The input will only have lower-case letters.
 * 1 <= dict words number <= 1000
 * 1 <= sentence words number <= 1000
 * 1 <= root length <= 100
 * 1 <= sentence words length <= 1000
 *
 *
 * @author Dingsheng Huang
 * @date 2020/3/27 21:15
 */
public class ReplaceWords {

    class TrieNode {
        TrieNode[] children = new TrieNode[26];
        String word = "";

        private void insert(TrieNode root, String word) {
            char[] chs = word.toCharArray();
            for (int i = 0; i < chs.length; i++) {
                int idx = chs[i] - 'a';
                if (root.children[idx] == null) {
                    root.children[idx] = new TrieNode();
                }
                root = root.children[idx];
            }
            root.word = word;
        }
    }




    public String replaceWords(List<String> dict, String sentence) {
        // construct trie
        TrieNode root = new TrieNode();
        for (String word : dict) {
            root.insert(root, word);
        }
        // traverse every word in the sentence
        String[] preset = sentence.split(" ");
        List<String> result = new ArrayList<>();
        for (String pre : preset) {
            result.add(process(pre, root));
        }
        StringBuilder stringBuilder = new StringBuilder();
        for (String item : result) {
            stringBuilder.append(item);
            stringBuilder.append(" ");
        }

        return stringBuilder.substring(0, stringBuilder.length() - 1);
    }

    private String process(String pre, TrieNode root) {
        // just thinking when we should return result !!
        char[] chs = pre.toCharArray();
        for (int i = 0; i < chs.length; i++) {
            int idx = chs[i] - 'a';
            if (root.children[idx] == null) {
                if (root.word.length() > 0) {
                    return root.word;
                } else {
                    return pre;
                }
            }
            if (root.children[idx].word.length() > 0) {
                return root.children[idx].word;
            }
            root = root.children[idx];
        }
        if (root.word.length() > 0) {
            return root.word;
        } else {
            return pre;
        }
    }


}