CodeGym/Help with Java Tasks/unraveling the mystery of the validator and requirements

Level 23

Szekesfehervar

06.10.2021
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unraveling the mystery of the validator and requirements

Question about the task

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The validator said me: "Be sure that the lines list has the ADDED label with the required lines in the correct places." I checked the program with the 22 test cases shown in the attached image and my program gives the outputs shown in red. (I made sure that this program would never be able to give consecutive ADDED/REMOVED pairings. And in my opinion it tags the lines correctly with the labels.) 1) Which case violates CodeGym's (unspoken?secret?) requirements, and how? What would be the correct output for the given incorrect case so that the validator can accept it? 2) Or an other option: what case did I forget to test that gives incorrect output?

Read 2 file names from the console: file1 and file2.
Both files contain text, but file2 is an updated version of file1. Some of the lines are still the same.
You need to create a merged version of the lines by writing them to the lines list.
The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label.
The example includes empty lines for clarity.
Neither the original file nor the updated file have empty lines!

Example 1:
original updated merged file1: file2: Result: (lines) line1 line1 SAME line1 line2 REMOVED line2 line3 line3 SAME line3 line4 REMOVED line4 line5 line5 SAME line5 line0 ADDED line0 line1 line1 SAME line1 line2 REMOVED line2 line3 line3 SAME line3 line4 ADDED line4 line5 line5 SAME line5 line0 REMOVED line0

Example 2:
original updated merged file1: file2: Result: (lines) line1 line1 SAME line1 line0 ADDED line0

In the example, empty lines mean that the line is not in the specified file.

Requirements:

The Solution class must contain a LineItem class.
The Solution class must have an enum called Type.
The Solution class must have a public static List<LineItem> field called lines that is initialized immediately.
In the main(String[] args) method, the program must read file names from the console (use BufferedReader).
In the main(String[] args) method, the BufferedReader used for reading input from the console must be closed after use.
The program must read the contents of the first and second file (use FileReader).
The file input streams (FileReader) must be closed.
The lines list should contain the merged version of the lines from the files. Each line should start with the label ADDED, REMOVED, or SAME, depending on the action taken.

package com.codegym.task.task19.task1916; /* Tracking changes */ import java.util.*; import java.io.*; public class Solution { public static List<LineItem> lines = new ArrayList<>(); public static void main(String args[]) throws Exception { ArrayList<String> origiList = new ArrayList<>(); ArrayList<String> updatedList = new ArrayList<>(); BufferedReader readConsole = new BufferedReader(new InputStreamReader(System.in)); String fileNameOrigi = readConsole.readLine(); String fileNameUpdated = readConsole.readLine(); readConsole.close(); BufferedReader origiFileRead = new BufferedReader(new FileReader(fileNameOrigi)); String line; while ((line = origiFileRead.readLine()) != null) { if (line.isEmpty()) break; origiList.add(line); } origiFileRead.close(); BufferedReader updatedFileRead = new BufferedReader(new FileReader(fileNameUpdated)); while ((line = updatedFileRead.readLine()) != null) { if (line.isEmpty()) break; updatedList.add(line); } updatedFileRead.close(); if (origiList.size()==0 && updatedList.size()>0) { added(updatedList.get(0)); System.out.println(lines); return; } if (origiList.size() > 0 ) { int remove = 0; for (int i=0; i<origiList.size(); i++) { if (updatedList.size() > i-remove) { if (origiList.get(i).equals(updatedList.get(i-remove))) { same(origiList.get(i)); /* */ if ((origiList.size() <= i+1) && (updatedList.size() > i-remove+1)) { added(updatedList.get(i-remove+1)); // System.out.println("itt-if"); } else { /* System.out.println("itt-else, "+remove); */ } } else { if (origiList.size() > i+1) { if (updatedList.size() > i-remove+1) { if (origiList.get(i+1).equals(updatedList.get(i-remove))) { removed(origiList.get(i)); same(origiList.get(i+1)); remove++; i++; } else { if (origiList.get(i).equals(updatedList.get(i-remove+1))) { added(updatedList.get(i-remove)); same(origiList.get(i)); remove--; } else { removed(origiList.get(i)); break; } } } else { if (origiList.get(i+1).equals(updatedList.get(i-remove))) { removed(origiList.get(i)); same(origiList.get(i+1)); if (origiList.size() > i+2) { removed(origiList.get(i+2)); break; } else break; } else {removed(origiList.get(i)) ; break; } } } else { if (updatedList.size() > i-remove+1) { if (origiList.get(i).equals(updatedList.get(i-remove+1))) { added(updatedList.get(i-remove)); same(origiList.get(i)); if (updatedList.size() > (i-remove+2)) { added(updatedList.get(i-remove+2)); break; } else break; } else { removed(origiList.get(i)); break;} } else {removed(origiList.get(i)); break;} } } } else { removed(origiList.get(i)); break; } } } // System.out.println(lines); } public static void added(String line) { lines.add(new LineItem(Type.ADDED, line)); } public static void removed(String line) { lines.add(new LineItem(Type.REMOVED, line)); } public static void same(String line) { lines.add(new LineItem(Type.SAME, line)); } public static enum Type { ADDED, // New line added REMOVED, // Line deleted SAME // No change } public static class LineItem { public Type type; public String line; public LineItem(Type type, String line) { this.type = type; this.line = line; } // @Override // public String toString() { // return type.toString()+"-"+line; // } } }

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Lisa

Level 41

7 October 2021, 15:38

Do you intentionally break when your files contain a empty line? Or is this by mistake?

Gellert Varga

Level 23 , Szekesfehervar, Hungary

8 October 2021, 19:18

This was completely intentional. According to the task description: "There are no empty lines in either the original file or the updated file!" So I had to make sure that if CG tested the program with tricky test files that have empty lines, my program would be able to refuse to read that empty lines.

Lisa

Level 41

8 October 2021, 19:40

yo, the do not test this, these are the requirements that CG adheres to in the tests. So eg your tests 4, 6 ,7, 8, 10 aren't necessary

Gellert Varga

Level 23 , Szekesfehervar, Hungary

8 October 2021, 20:13

About cases 4, 6, 8, 10, 12, 14: The requirement said: "The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label." Reading this very vague description of the task, one cannot be sure what this means of the following two options: 1) Maybe CG guarantees us that, in the cases they check, original.txt and updated.txt will always contain only text that does not allow such output: ADDED,ADDED; or REMOVED,REMOVED; etc. 2) Maybe I, the future programmer, must guarantee that no such sequence of output can ever occur: ADDED, ADDED; or REMOVED,ADDED; etc. I chose the second option:) If such file content occurs, my code breaks the output.

Guadalupe Gagnon

Level 37 , Tampa, United States

7 October 2021, 13:19

solution

Testing out your code I found an incorrect output. Try this: File1: aaa bbb ccc File2: aaa ccc ddd The "lines" list should be: [SAME-aaa, REMOVED-bbb, SAME-ccc, ADDED-ddd] but it is outputting: [SAME-aaa, REMOVED-bbb, SAME-ccc]

Gellert Varga

Level 23 , Szekesfehervar, Hungary

8 October 2021, 19:18

Thank you very much for your detection! This test case had escaped my attention... and this case did indeed give an incorrect output. I had to add a newer bifurcation option to one of the pathes of the flowchart drawn on paper, and after correcting the program, the validator could not mess with my solution.:) However, this task involved several days of work for me. I would be interested to know how others have done this task. Because I have the feeling that my solution is extremely complicated...

Guadalupe Gagnon

Level 37 , Tampa, United States

8 October 2021, 19:23

I had problems with this task when I first did it too. See my post here (and how overly complicated my code was)

Lisa

Level 41

8 October 2021, 19:35

Mine is not representative either cause I played around and wrote an Iterator that returned the result for each line that's without the business logic, the iterator itself.... and the solution is probably always complicated

public static void main(String[] args) {
        List<String> linesFile1, linesFile2;
        try (BufferedReader console = new BufferedReader(new InputStreamReader(System.in))) {
            linesFile1 = readToList(console.readLine()); // using an own method instead of readAllLines cause CG requires a FileReader
            linesFile2 = readToList(console.readLine());
        } catch (IOException ioe) {
            throw new RuntimeException();
        }

        // we need at least 1 element in each list otherwise a comparison is useless
        if (linesFile1.size() < 1 && linesFile2.size() < 1) {
            throw new IllegalArgumentException("Not enough lines for a comparison");
        }

        // create a LineComparator object, passing listIterators of the lists of the read files and iterate over that Linecomparator
        LineComparator lc = new LineComparator(linesFile1.listIterator(), linesFile2.listIterator());
/*
        Iterator<LineItem> lit = lc.iterator();
        while (lit.hasNext())
            lines.add(lit.next());
*/
        // or just
        for (LineItem lineItem : lc) lines.add(lineItem);

        // debug code
        // lines.forEach(e -> System.out.println(e.type + " ==> " + e.line));
    }

    // reads a file into a list
    private static List<String> readToList(String fileName) throws IOException {
        List<String> retVal = new ArrayList<>();
        try (BufferedReader in = new BufferedReader(new FileReader(fileName))) {
            while (in.ready())
                retVal.add(in.readLine());
        }
        return retVal;
    }

Gellert Varga

Level 23 , Szekesfehervar, Hungary

8 October 2021, 19:54

@Lisa: You wrote: " // we need at least 1 element in each list otherwise a comparison is useless" This overlaps what the requirement says: "Neither the original file nor the updated file have empty lines!" Nevertheless, I don't know why, but I solved the problem so that if one file is completely empty and the other file has only one line, it displays the correct result "ADDED" or "REMOVED". It passed.:)

Gellert Varga

Level 23 , Szekesfehervar, Hungary

8 October 2021, 20:19

@Lupe: Sorry, but at the moment I (still) have absolutely no idea how your code works... But I would definitely like to ask you what is the role of the Chinese character (亦) you used?

Guadalupe Gagnon

Level 37 , Tampa, United States

8 October 2021, 20:30

It was a crazy idea I had back when I was learning. Adding characters from a charset that definitely wouldn't be used by the validation system for the English tasks as an easy way to separate things I added to a String from the String itself. This made splitting it afterwards easy to be exact. It really just added way more complexity to something that should have been simple, but i was learning at the time.