CodeGym/Help with Java Tasks/Why is this solution not working.

Level 8

Newbury

21.05.2019
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10comments

Why is this solution not working.

Question about the task

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I have tested the code with different inputs and it gives the right output but not passing the most tests in codegym. I also tried changing List<String> to ArrayList<String> in the instant variable still no luck. Anybody please explain what I am doing wrong here? Thanks.

1. Create a list of strings.
2. Read 5 strings from the keyboard and add them to the list.
3. Using a loop, find the shortest string in the list.
4. Display the string.
5. If there is more than one, display each on a new line.

Requirements:

Declare a string list variable and immediately initialize it.
The program should read 5 strings from the keyboard and write them to the list.
The program should display the shortest string.
If several strings are the shortest, then you need to display each of them on a new line.

package com.codegym.task.task07.task0709; import java.util.*; import java.io.*; class Solution { private static List<String> list = new ArrayList<String>(); public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); ArrayList<String> shortWords = new ArrayList<String>(); String shortest = ""; for(int i = 0; i < 5; i++) { list.add(reader.readLine()); } Collections.sort(list); shortest = list.get(0); for(int j = 1; j < list.size(); j++) { if(shortest.length() == list.get(j).length()) { shortWords.add(list.get(j)); } } shortWords.add(shortest); for(String temp : shortWords) { System.out.println(temp); } } }

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Hoang Khai

Level 8 , Chantilly, United States

17 July 2019, 20:52

May be you are required to sort using loops. If you use the built in function, it will not work. I think so.

Djole

Level 41 , Belgrade, Serbia

21 May 2019, 09:51

you need to sort list by length of words, not alphabetically.

Raivo Lapiņš

Level 18 , Riga, Latvia

21 May 2019, 10:30

Basically this is the issue here. In some cases longer word will be stored as first element since it is sorted alphabetically. For example if we take input:

aaaa
aao
aal
aak
aita

Then the given output will be:

aita
aaaa

which is wrong. If we take a look and debug your code with given inputs then after calling sort() method on your list the sorted list looks like this:

From here on you can see that the conditions in your loop will not be met to get correct output.

Show How

Level 8 , Newbury, United Kingdom

21 May 2019, 11:19

Hi, thanks for your reply. I have edited the code and it still not passing. Can you please explain what is wrong with it?

import java.util.*;
import java.io.*;

class Main  {

  private static List<String> list = new ArrayList<String>();

  public static void main(String[] args) throws Exception {
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    ArrayList<String> shortWords = new ArrayList<String>();
    String shortest = "";
    for(int i = 0; i < 5; i++) {
      list.add(reader.readLine());
    }

    Collections.sort(list);
    shortest = list.get(0);

    for(int j = 1; j < list.size(); j++) {
      if(shortest.length() == list.get(j).length()) {
        shortWords.add(list.get(j));
      }
      else {
        if(shortest.length() > list.get(j).length()) {
          shortest = list.get(j);
        }
      }
    }

    shortWords.add(shortest);

    for(String temp : shortWords) {
      System.out.println(temp);
    }

  }
}

Raivo Lapiņš

Level 18 , Riga, Latvia

21 May 2019, 11:41

To be fair I just went over my own code that passed testing and found a mistake. For the inputs that I mentioned above my code doesn't work. So it seems that their internal testing could be wrong in this particular case. I will supply my code since it actually isn't correct for this task and it shouldn't be counted as giving a solution:

ArrayList<String> list = new ArrayList<>();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
for(int i = 0; i < 5; i++){
    list.add(bufferedReader.readLine());
}

Collections.sort(list);
for(int i = 0; i < list.size(); i++){
    int shortestLen = list.get(0).length();
    if(list.get(i).length()<=shortestLen){
        System.out.println(list.get(i));
    }
}

See if it passes the testing. Edit: I just went over the task again and implemented double for loops to sort the strings starting from the shortest and then display the correct result. As funny as it is I can't pass the testing. Something must be wrong at their end in my opinion.

Show How

Level 8 , Newbury, United Kingdom

21 May 2019, 12:12

Hi, thanks again for your reply. I tried your code and now it fails only because of the 2nd condition which sound stupid as it says "The program should read 5 strings from the keyboard and write them to the list.". I have even tried with Comparator interface which works fine as of before without it but not passing.

Raivo Lapiņš

Level 18 , Riga, Latvia

21 May 2019, 12:17

Yeah, I would probably contact the site owners and point out this mistake and proceed with other tasks. Kind of weird that my code passed testing, although it's wrong and you can't pass the tests with same code. P.S. You try to test from IntelliJ or web compiler?

Show How

Level 8 , Newbury, United Kingdom

21 May 2019, 12:19

Thanks for your quick reply and insight. I will send them my codes and as you suggest proceed with other tasks. Have a good day.

Show How

Level 8 , Newbury, United Kingdom

24 May 2019, 11:02

Hi, I have solved the issue by just moving the ArrayList variable in the main method and all tests are passed. Thanks for your help.

Turner

Level 11 , Pittsburgh, United States

16 August 2019, 19:18

That is because the initial requirement says that ArrayList<String>strings must be immediately initialized. Static variables are initialized OUTSIDE of the Main program and that is probably tripping the verification. Hope the explanation is clear. The real bug in this example is not being about to use List<String>strings. The verification is forcing you to specify what kind of List class to use. Totally unnecessary.