Geekflex

Do you specify that you can’t use any functions?

Otherwise why wouldn’t they just write something like this:

function findLastIndex( String stringParam, int ch) { int retVal = -1;

if( !"".equals(stringParam) ) {
     retVal = stringParam.lastIndexOf(ch);

} return retVal; }

I’d personally not check for null, but I would clearly state that the function assumes as a precondition that the input must be a valid, none-null string. DbC ftfw. Saves a check for null, promotes dynamic programming, shows you’re smart and leaves the bugs at the caller’s side. So long as you’re (I’m) clear about the preconditions.

As for starting the search at the end of the string, I fear I might fall prey for rushing into coding and immediately start at the beginning. But I have no doubt I’d see this soon after I (start to) code.

I think I’d ask about the char-not-found case sooner rather than later. I’d probably also ask about integer overflows, should the string be too long. Java strings aren’t null-terminated, but it’s worth mentioning the case where the char is null. (Shh, I just googled to settle my in-confidence about the end of a string in Java, but don’t tell anyone). I’d also mention the case of multibyte or variable-width string encoding, even though Java supposedly takes care of this for you. I just don’t like to be spoon-fed, so I like being conscious of these things.

I’d mention my code is thread-safe in allowing multiple threads to operate on the same string, so long as the string is not modified by some other function outside the scope of the threads. I’d mention the function poses a no-throw exception safety.

The case of an empty string is the exact same case as that where the char can’t be found.

All this and more in my wild, wet dreams where I actually do well when people watch and judge me. Alas, I am widely known for FAILing kindergarten-anything when I’m nervous.

Turns out you are right..I feel like I used to use this condition before and it worked. Maybe I was using StringUtils.isBlank(). This just goes to show you what happens when you stop coding for a while.

I think you’re going into too much detail with a lot of those points (your C++ background is showing ;-)), for a toy problem on an interview anyway.

Mentioning that the string is assumed not to be null is ok, it shows that you thought of it and that’s what’s really important. Even better would be throwing an IllegalArgumentException or making the function return -1.

If someone started from the beginning of the string the first time (most people do) then I would expect them to notice that they could/should start at the end, or I would ask them to walk through an example with a super long string and see if they figure it out.

Strings are immutable in Java, and chars are passed by value, so your function would be thread safe by default. And yes, ALL strings in Java are UTF-16 so they are double-wide and you don’t have to think about it. Also, you cannot get an integer overflow from a string length; Java strings can’t be that long.