Suppose we have the following state:
| S | T |
| S | H |
S is the body of the snake, H is the head of the snake, and T is the tail of the snake.
If I want to move the head to the Tail position (i.e. an 'U' move), it is a valid move ONLY IF there is NO food at the tail position.
i.e. the snake doesn't remove its tail if it eats food
Hope this could help anyone who is struggling on the last test case!