Does your solution work correctly locally for input of {{}}?

You can post your code here (see how: https://docs.codewars.com/training/troubleshooting#post-discourse) so someone could take a look.

Same thing. Based on shown tests, everything is fine locally. No exceptions are thrown.

getting the same error, anyone know how to fix it?

SEGV indicates that there is a segfault. If you are programming in C++, then I suggest to use std::runtime_error to gather information about your problem. Also note that the test case {{}} is initialized as {std::vector({})}.

Getting the same error although visual assist runs it just fine.

UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000000000000 (pc 0x00000042c8ba bp 0x0000021f7100 sp 0x7ffd9b0c80a0 T1)
==1==The signal is caused by a READ memory access.
==1==Hint: address points to the zero page.
==1==WARNING: invalid path to external symbolizer!
==1==WARNING: Failed to use and restart external symbolizer!
#0 0x42c8b9 (/workspace/test+0x42c8b9)
#1 0x425597 (/workspace/test+0x425597)
#2 0x428213 (/workspace/test+0x428213)
#3 0x4269ee (/workspace/test+0x4269ee)
#4 0x426549 (/workspace/test+0x426549)
#5 0x42613b (/workspace/test+0x42613b)
#6 0x42c4f5 (/workspace/test+0x42c4f5)
#7 0x42585d (/workspace/test+0x42585d)
#8 0x7fea57989bf6 (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
#9 0x404589 (/workspace/test+0x404589)

UndefinedBehaviorSanitizer can not provide additional info.
==1==ABORTING

I dont't understand why I have this error