CodeSignal Solution rearrangeLastN

rearrangeLastN

# Definition for singly-linked list:
# class ListNode(object):
#   def __init__(self, x):
#     self.value = x
#     self.next = None
#
def rearrangeLastN(l, n):
    if n == 0:
        return l
    front, back = l, l
    for _ in range(n):
        front = front.next
    if not front:
        return l
    while front.next:
        front = front.next
        back = back.next
    out = back.next
    back.next = None
    front.next = l
    return out