what does segmentation fautl (core dumped) means?

Question

After i gave input to merge sort and this error appears

Answer 1

segmentation fault is an error that occurs when you try to access memory that you don't have access to (if that makes sense for some reason).
for example, when you try to dereference a null pointer, or write on a read only memory and others.
hope this helped a bit, perhaps others will come with more explanations

Answer 2

thanks i aslo think that memory issue was there as i was running the code on online compiler.