I was really happy with my solution. HOW is it wrong?

Question about the task

Under discussion

This has been probably the most frustrating chapter yet with validation. I've tested numerous data sets with my algorithm. It tries starting with all words in the list and returns the longest result. It's worked with everything I've thrown at it, even the ones you guys have suggested. I think the most frustrating part of CodeGym is we don't get to see the dataset that's failing validation. I wish they would provide the test samples they use so I can SEE where my results differ from theirs. Since that's not possible, anyone have any explanations?

In the main method, read the name of a file that contains words separated by spaces from the console.
In the getLine method, use StringBuilder to order all the words as follows: the last letter of a word must match the first letter of the next word (ignore case).
Each word should be used once.
The getLine method can return any variant.
Separate words with a space.
Display the resulting string on the screen.

Example input file:

Okinawa Washington Auckland Kalamazoo Norfolk

Result:

Washington Norfolk Kalamazoo Okinawa Auckland

Requirements:

The main method must read the filename from the keyboard.
There should not be static fields in the Solution class.
The getLine method must use StringBuilder.
The getLine method must return an empty string (an empty StringBuilder) if it is not passed arguments (words).
The getLine method must not change the arguments (words).
All words passed to the getLine method must be included in the resulting string, if possible.
The screen output must match the task conditions.

package com.codegym.task.task22.task2209; /* Make a word chain */ import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class Solution { public static void main(String[] args) throws IOException { List<String> words = new ArrayList<>(); BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); BufferedReader fileReader = new BufferedReader(new FileReader(reader.readLine())); reader.close(); while (fileReader.ready()) { words.addAll(Arrays.asList(fileReader.readLine().trim().split(" "))); } fileReader.close(); StringBuilder result = getLine(words.toArray(new String[words.size()])); System.out.println(result.toString()); } public static StringBuilder getLine(String... words) { if(words == null || words.length == 0) return new StringBuilder(); List<StringBuilder> allWordCombos = new ArrayList<>(); for(int i = 0; i < words.length; i++) { //Remember this code below. This was tricky to cast to ArrayList //Arrays.asList returns List, and we can't just do (ArrayList<>) Arrays.asList(words); List<String> remainingWords = new ArrayList<>(Arrays.asList(words)); StringBuilder result = new StringBuilder(); result.append(remainingWords.remove(i)); while(!remainingWords.isEmpty()) { char lastChar = result.charAt(result.length() - 1); String nextWord = findNextWord(remainingWords, lastChar); if(nextWord != null) { result.append(" "). append(nextWord); remainingWords.remove(nextWord); } else break; } allWordCombos.add(result); } StringBuilder finalResult = allWordCombos.get(0); for(StringBuilder s : allWordCombos) if(s.length() > finalResult.length()) finalResult = s; return finalResult; } public static String findNextWord(List<String> remainingWords, char lastChar) { for(String s : remainingWords) if(Character.toLowerCase(lastChar) == Character.toLowerCase(s.charAt(0))) return s; return null; } }

Comments (4)

Popular
New
Old

You must be signed in to leave a comment

Guadalupe Gagnon

Level 37 , Tampa, United States

6 March, 18:35

I see the logic of your code in that you take each word in the passed in list, build a result by chaining off of that word, adding it to a list of all results, then find the longest "result" to pass back as the answer. The problem however, is that by finding the next word by using the last char of the last word added to the temp list that is being built, the final result is built in only one direction. This is a problem when there are words that could fit in the middle of the result. Take, for example, if you tested the code with the words: "hat temple hannah hatch" When I run this code I end up with an output result of: hannah hat temple But the word "hatch" should be between "hannah" and "hat" so the correct result would be: hannah hatch hat temple Which is why the "All words passed to the getLine method must be included in the resulting string, if possible." condition is not validating. You could probably fix this code by adding an additional step before line 52 that tests any words left over in remainingWords to see if they fit in the middle of result before being added to allWordCombos

Rich Piske

Level 30 , United States of America, United States

7 March, 06:24

Thank you for the super thoughtful reply! You make a good point, and I will explore your suggestion. I’ll say again, this is why I wish they would give us the different datasets they use to validate. It would make my life so much easier.

Guadalupe Gagnon

Level 37 , Tampa, United States

7 March, 14:27

I have been on this site since 2018. They polled me sometime around 2019 or 2020 and when they asked what they could do better I specifically recommended having a system like other coding websites (such as leetcode) where you can enter test data, run it with your code, and it gives the result(s) of your code as well as the actual correct result(s) of that test data. When verifying on leetcode, when you fail, it will give you the single data that your code didn't process correctly from its test data set. This gives you an idea of where the failure point of your code is and you end up learning a lot on problem solving rather than being stuck for days on a task because instead of a problem with your algorithm you used an l instead of an I (lowercase L and capital i). This seems like an easily avoidable mistake but people who don't speak English make this mistake all the time since core Java is in English.

Rich Piske

Level 30 , United States of America, United States

6 March, 01:04

Not sure why the validation results didn't carry through. The requirement failed is: "All words passed to the getLine method must be included in the resulting string, if possible."