String Chain

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;



class Result {

    /*
     * Complete the 'longestChain' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts STRING_ARRAY words as parameter.
     */

    public static int longestChain(List<String> words) {
        if (null == words || words.size() < 1) {
            return 0;
        }

        int maxChainLen = 0;

        HashSet<String> hash = new HashSet<>(words);
        HashMap<String, Integer> wordToLongestChain = new HashMap<>();

        for (String word : words) {
            if (maxChainLen > word.length()) {
                continue;
            }
            int curChainLen = find_chain_len(word, hash, wordToLongestChain) + 1;
            wordToLongestChain.put(word, curChainLen);
            maxChainLen = Math.max(maxChainLen, curChainLen);
        }
        return maxChainLen;
    }

    static int find_chain_len(String word, HashSet<String> words, HashMap<String, Integer> wordToLongestChain) {
        int curChainLen = 0;

        for (int i = 0; i < word.length(); i++) {
            String nextWord = word.substring(0, i) + word.substring(i + 1);
            if (words.contains(nextWord)) {
                if (wordToLongestChain.containsKey(nextWord)) {
                    curChainLen = Math.max(curChainLen, wordToLongestChain.get(nextWord));
                } else {
                    int nextWordChainLen = find_chain_len(nextWord, words, wordToLongestChain);
                    curChainLen = Math.max(curChainLen, nextWordChainLen + 1);
                }
            }
        }

        return curChainLen;
    }

}

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int wordsCount = Integer.parseInt(bufferedReader.readLine().trim());

        List<String> words = IntStream.range(0, wordsCount).mapToObj(i -> {
            try {
                return bufferedReader.readLine();
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            }
        })
            .collect(toList());

        int result = Result.longestChain(words);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}