[throwawaymath]

I understand the class of rebuttal you're invoking here, but reversing a string is extremely easy - with or without a library. This is not an academic problem designed to see if a person can study prior to an interview. This is a first pass question designed to see if a person is even acquainted with basic programming. Any such question you could devise would be similarly patronizing or orthogonal to the exact work done on the job.

And yet, despite how easy the question is people still fail it. It's frankly absurd to me that a senior software engineer can fail this question. It's practically a freebie slam dunk for anyone with basic competency. Briefly drop that you can use your language's core function or method to do it. Then declare a new array and iterate through the string backwards, appending each character to the new array. When you're done, collapse the array to a string.

In other words, it's testing if you can write a for loop. How many times in your job do you expect to implement a for loop? I use for loops quite often.

[jen20]

> iterate through the string backwards

What about multi-byte characters?

[zbentley]

That would be an excellent question to ask during an interview.

If you were interviewing with me, I'd ask you to do the (usually expected) ASCII/array-of-graphemes version first. If you did that, you'd pass, and get a positive shout-out in the feedback session for asking about multibyte chars.

If you, after solving the array-based form, had some ideas or even working code for how to handle multibyte characters directly, without falling back to the standard library of $language's idea of "what is an iterable character-equivalent unit in a string", and demonstrated similar insight in your other interview problems, I'd give a positive shout-out with the addendum that we might be interviewing you for the wrong (too junior) position.

In my experience, most people don't ask about multibyte chars. That's fine, if they solve the problem. It's not a positive or negative. If an interviewer is building questions with hidden "must-ask" gotchas like that, I think they're doing themselves and their candidates a disservice.

Something interesting does happen occasionally when candidates do ask about byte-width (or equivalent less-common but still very important gotchas like pointer/word size, endianness, etc. in relevant problems): some people ask the question, solve the naïve form of the problem, and then offer some thoughts as to how they'd handle the broader multibyte case. But some other people act as if knowing that gotcha means they won't or shouldn't have to continue solving the problem. I've had candidates tell me that they "figured it out" and wanted to go on to the next challenge at that point, without writing a line of code. I've had candidates tell me flat out that writing non-Unicode aware string processing algorithms was unrealistic and a waste of time, and that they wanted a problem that was more real-world or suited to their level of skill. Those things will also get you a shout-out in the interview review session, but not the good kind.

[kamaal]

>>Then declare a new array and iterate through the string backwards, appending each character to the new array. When you're done, collapse the array to a string.

a. You can't iterate a 'String' backwards. You need to know the length first. And that requires traversing the string forwards at least once.

b. Once you reach the end you are wasting the effort of revisiting the elements, since you visited them already once.

c. A better option is build a build a double linked list, as you are traversing the list forward.

d. Once you have the double linked list ready, you have pointers to both start and end, and you traverse the way you like.

e. An even better way would be to design a data structure that contains all this meta data at String creation itself.

    Class CustomString {
        char* headPointer;
        char* tailPointer;
        int length;
        bool isPalindrome;
        char* string;
        /* Add your interview acrobatic things here */
    }

Stuff like this.

Now even though the answer in your comment is correct, they could reject you for not coming up with the answers I gave from point a through e above.

Now imagine some one telling you that, on these grounds, you don't know a semicolon worth programming and are probably a liar.

I hope you understand what's going on here. Every body can be rejected if they don't cut through your cookie cutter.

[zbentley]

> a. You can't iterate a 'String' backwards. You need to know the length first. And that requires traversing the string forwards at least once.

That's not at all true in many languages. If a candidate asked "is this string's length known without an O(N) operation on the number of characters in it?" (or knew the answer for the default string constructs in the language they were using for the problem) I'd consider that a positive indicator. If they said what you just said, without consideration for the context, I'd consider that a negative.

This is not a case of someone expecting a given "cookie cutter" solution. Interviewers who do that are doing themselves and their candidates a disservice. This is a case where statements like "I know how strings work because I know how they work in $context" where $context is not what the interview expects you to work in will make a bad impression.

[tome]

It was supposed to be in Java.