Question

I’m having a problem and can’t seem to find the solution..

int linearSearch(nodeptr list,char search){
    int pos =0;
    if(list==NULL)
        return -1;
    while(list->info!=search && list!=NULL){
        pos++;
        list=list->next;
    }
    if(list==NULL)
        return -1;
    else
        return pos;
}

I always get a runtime error.. 🙁

Answer 1

while(list->info!=search && list!=NULL)

should be:

while(list!=NULL && list->info!=search) 

This is called as Short-circuit evaluation.
When you use && the first expression is guaranteed to be executed before the second for inbuilt primitive types^[#1].

In your case the dereferencing happens before the NULLcheck, So when list == NULL, You will end up derefrencing the NULLand causing an Undefined Behavior and a crash.

In the sugeested solution:
if list == NULL then the second condition will not be evaluated.

---

Reference:
^[#1]C++03 Standard 1.9.18:

In the evaluation of the following expressions

a && b
a || b
a ? b : c
a , b

using the built-in meaning of the operators in these expressions, there is a sequence point after the evaluation of the first expression (12).