Snake game

Simulate the Snake game on a width x height grid. The snake starts length 1 at cell (row 0, col 0) and you process a list of moves, each 'U','D','L','R'. food is a list of [row, col] cells that appear in order; eating the current food grows the snake by one and advances to the next food. A move returns the current score (length-1), or -1 if the snake hits a wall or its own body, after which the game ends. Return the list of results per move. The snake's tail vacates its cell on a non-eating move (so moving into the old tail cell is allowed).