In-Place String Reverse in C

Question

I am trying to learn the fundamentals of C, but I cannot figure out why this code doesn\'t work. The while loop in reverse() causes a bus error. I found almost identical code

Answer 1

The problem is that you're trying to reverse a constant literal string, which is read only. Change the declaration of a in main to char a[] = "12"; to make it a writable char array instead

Answer 2

You are trying to change a string literal which leads to undefined behavior.

Change

char* a = "12";

to

char a[] = "12";

Answer 3

Because end and str point to the same memory location -> they're two different names of the same object. You can avoid using two variables:

char foo[20] = "abcdefghi", tmp;
int counter = 0, length = strlen(foo);

for(counter, counter < length / 2; counter++) {
    tmp = foo[counter];
    foo[counter] = foo[length - counter];
    foo[length - counter] = tmp;
}