Ruben Safir ruben.safir-at-my.liu=
.edu writes:

but pos2 and pos3 change throughout t=
he merge loop. What you=E2=80=99re comparing them to is supposed to stay fi=
xed.

where?

Here=E2=80=99s the code you had:

ceCode cpp">for(i =3D 0=
; i < length; i++)
{
   if(pos1 < pos2 && ( pos2 =3D=3D pos=
3 || max(in[pos1], in[pos2]) =3D=3D in[pos1]))
   {
      space[i] =3D in[pos1];
      pos1++;
   }
   else
   {
      space[i] =3D in[pos2];
      pos2++;
   }
}

Obviously, pos2 is changing throughout that loop, because i=
t says pos2++. (This has nothing to do with the recursion.) In=
the if, what you=E2=80=99re comparing pos1 to sh=
ould stay the same.

Here it is with my bug fix:

ceCode cpp">for(i =3D 0=
; i < length; i++)
{
   if(pos1 < left+mpt && ( pos2 =3D=3D=
 right || max(in[pos1], in[pos2]) =3D=3D in[pos1]))
   {
      space[i] =3D in[pos1];
      pos1++;
   }
   else{
      space[i] =3D in[pos2];
      pos2++;
   }
}

The pos1 and pos2 are indeed =E2=80=9Ccursors=
=E2=80=9D working through the two lists. Both of them move. The pos1<=
/code> gets to the end of its list when it equals left+mpt. Th=
e pos2 gets to the end of its list when it equals right<=
/code>.