Getting IndexOutOfBoundExceptions when trying to create a new string array out of strings that contain chars and integers

Question

I was asked the following question in an interview today which asks us to write a small program that checks whether two text sources might be in fact the same.

I was able to get a solution for checking whether two strings were the same length, otherwise, it's not a match. However, I tried to come up with a solution where I would first create a "filtered" array, that is, convert, for example A2Le to A..Le and then comparing it to 2pL1 which when filtered is ..pL.. And I failed horribly there. Attached is my attempt:

    int SLength = 0;
    int TLength = 0;

    String[] SParts = S.split("[^\\d]+");
    String[] TParts = T.split("[^\\d]+");

    for(int i = 0; i < SParts.length; i++) {
        if(!SParts[i].equals("")){
            SLength += Integer.parseInt(SParts[i]);
        }
    }

    for(int i = 0; i < TParts.length; i++) {
        if(!TParts[i].equals("")){
            TLength += Integer.parseInt(TParts[i]);
        }
    }

    for(int i = 0; i < S.length(); i++) {
        if(!Character.isDigit(S.charAt(i))){
            SLength += 1;
        }
    }

    for(int i = 0; i < T.length(); i++) {
        if(!Character.isDigit(T.charAt(i))){
            TLength += 1;
        }
    }

    if(TLength != SLength) {
        return false;
    }

    // Convert String S from "A2Le" to "A..Le"
    char[] sArray = S.toCharArray();
    char[] sArrayFiltered = new char[SLength + 1];
    int sIndex = 0;
    for(int i = 0; i < sArray.length; i++) {
        if(Character.isDigit(sArray[i])) {
            sIndex += Character.getNumericValue(sArray[i]);
            System.out.println("Digit Index: " + sIndex + ", Char: " + sArray[i] + ", Index: " + i);
        } else {
            sArrayFiltered[i] = sArray[sIndex];
            sIndex++;
            System.out.println("Char Index: " + sIndex + ", Char: " + sArray[i] + ", Index: " + i);
        }
    }

I kept getting IndexOutOfBoundExceptions like this:

Char Index: 1, Char: A, Index: 0
Digit Index: 3, Char: 2, Index: 1
Char Index: 4, Char: L, Index: 2
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
    at ReverseString.solution(ReverseString.java:192)
    at ReverseString.main(ReverseString.java:210)

This example used the A2Le sample string.

I tried to step my code through the debugger, but that did not seem to help me out.

EDIT: I know what the cause of the OutOfBoundException is - but not why it is being caused in the context of this problem. I'm not asking why I have an OutOfBound, but where.

@Tom I know what the cause of the error is, but I don't know how to solve it in the context of this problem. — theGreenCabbage, Mar 28 '16 at 20:56

score 2 · Accepted Answer · answered Mar 28 '16 at 20:52

2

sArray has a length of 4 so the last index is 3.

At the following line, sIndex's value is 4, the index for does not exist, hence the exception.

sArrayFiltered[i] = sArray[sIndex];

I think the flaw in the logic is the following line

sIndex += Character.getNumericValue(sArray[i]);

Why add the numeric value to sIndex ?

answered Mar 28 '16 at 20:52

Yassin Hajaj

21,337
9
51
89

Thanks! Let me look into it. I added the numeric value to `sIndex` because that is the index of `sArrayFiltered`, which will represent my string `A??Le`. – theGreenCabbage Mar 28 '16 at 20:58
Oh wow. You are totally right. That was the offending line.. The solution should have been `sArrayFiltered[sIndex] = sArray[i];`. I mixed it up during the pressure of the interview. Thank you Yassin! – theGreenCabbage Mar 28 '16 at 21:01
@theGreenCabbage You're welcome ! Good luck with that :) – Yassin Hajaj Mar 28 '16 at 21:02

Getting IndexOutOfBoundExceptions when trying to create a new string array out of strings that contain chars and integers

1 Answers1