C++ question with pointers

Question

//Please someone can give me a logical explanation why this code gives -1 as result??
// and what is the value of t, p1 and p2...??; it seems an ambiguous problem

int t[4]={8,4,2,1};

int *p1 = t+2, *p2 =p1-1;

p1++;

cout<<*p1-t[p1-p2];

Answer 1

thanks for the answers it clears me up more

Answer 2

When you write p1++ you are moving the pointer in memory not changing its value. Then anything can happen.

You probably want

(*p1) ++

If you want to know about moving pointers google Pointer Arithmetic