You should read again how BF works. It operates on some memory cells and , writes memory to output, while . reads input to memory. Your code only works on input and output.

The logic of your code handles well when it compares NORTH against SOUTH or EAST against WEST (or viceversa), but doesn't when you need to go in the same direction twice in a row. Try to test for those scenarios. Example, you are given this array: |NORTH -> NORTH -> WEST -> WEST|;
And compare how it behaves with this other array: |NORTH -> SOUTH -> EAST -> WEST|;
Analize the outcome of both.

For what I can see, you are almost done. You just have to think what will happen, let's say, for example, going north twice.