True, but O(4N) == O(N), so it's still linear (although inefficient).

This solution is great but works only for "example !" and not for "example!"

isn't the complexity of this solution 4N? wouldn't it be better to use just a for loop and 4 variables for counting nsew?

Change one of the base test cases to the one from exercise example and print the population number after each iteration.. Think you guess

So? It's not right. Not a kata issue. See the example in the kata's description, find what you're doing wrong.