Removing a substring from a char array without using any libraries in C

Question

I am a computer science first year student and our teachers gave a binary pattern search task to do. We have to remove a substring from a string without using any libraries and built-ins like(memmove or strstr). Our only hint is that its something to do with '\\0'. I don't see how we are going to achive this because as i know the null character only ends a string not removes it. And given an unknown input it gets even harder to get around. I need help about the usage of null character. EDIT: Oh and also we are not allowed to create new arrays. EDIT2: The problem is much more complicated if you are here for the solution read the comments under this thread and the marked solution's also.

Answer 1

C strings are "null terminated" which means they are considered to end wherever a null (written '\\0' in C) appears.

If I start with the string "Stack Overflow" and I overwrite the space with '\\0' , I now have the string "Stack". The storage for "Overflow" still exists, but it is not part of the string according to C functions like strlen() , printf() etc. In fact, if I hold a pointer to the "O" part of the original string, it will be just as if there are two strings: "Stack" and "Overflow", and you can still use both of them.

It's like if I come to where you live and I build a huge wall across the road just before your house. The road is now shortened, and people on my side of it won't know you are there.