def every_other_rev(xs: list[int]) -> int:
# xs[::-2] — reverse, then take every 2nd element.
return sum(xs[::-2])
def every_third_rev(xs: list[int]) -> int:
return sum(xs[::-3])
def full_reverse(xs: list[int]) -> int:
# xs[::-1] still routes through the reverse path.
return sum(xs[::-1])