Impressive!

The test cases for this problem do not cover instances when x or y could be strings in case of subtraction, divison or multiplication. Ideally, you would first check if x and y are ints, and not allow any operation if it they are any other type. In your case, you only cover addition with this type check. If I were to input strings in x or y with -, *, or /, it would produce a type error.

I'd take hard coding instead of hard scrolling :D

Got to appreciate the effort

I think it can be clearer to explicitly mention or hint that evaporating part will keep changing, i.e. ex. 10% of leftover gas. It is not a fixed amount.

Exit code 139 usually means segmentation fault. This means that you program is trying to access some part of memory which is not allocated for this program. Most frequent case of this is trying to access undefined index of an array. You should check if all of your boundaries are properly checked for. If you are interested, here are a couple of resources to check out:
https://www.geeksforgeeks.org/core-dump-segmentation-fault-c-cpp/
https://stackoverflow.com/questions/15600296/counter-exit-code-139-when-running-but-gdb-make-it-through
https://kb.iu.edu/d/aqsj

It might be useful to specifically stress the importance of the fact that only one number will appear odd number of times within an array. Current description can be also understood as one of the numbers is different, as odd sometimes is referred to as "different". While the task is not difficult, it might help new guys to understand it better

Hope your students liked it :)

There are more ways to convert double to integer: https://javarevisited.blogspot.com/2017/01/how-to-convert-double-to-int-in-java.html
Whichever seems more convenient :)

This kata seems to be too easy for 8kyu. Petition to move it down to 10kyu :D

The description can be a little bit clearer. When submitting to tests, after a while you recognize that it needs checks for exceeding step length and whether begin is greater than end.

This kata is good for practicing recursion on. I think it can have its place in 4kyu.

Damn straight :)