add << std::flush after the values you print. flushing the standard output ensures you will see it even if the program crashes

This part, and specifically the READ at 0x000000000000, usually means that the error is caused by reading a past-the-end iterator:

==1==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000000000000 [...]
==1==The signal is caused by a READ memory access.

Note that in this kata it is possible to receive "" as an input (don;t ask me why), and it should be treated as "0".

Ideally, failed tests would present the input which made them fail. But if they do not, you can try this: https://docs.codewars.com/training/training-example#debugging-a-kata

[[1, 2], [0, 2], [0, 2]] is what your solution returned. If you want to see the input, you can print it.

All correct, but the test input is 987654310.

Cheers :)

It is not the next greatest compared to the test input...