For linked list 1->2->3, the reversed linked list is 3->2->1
Solution
"""
Definition of ListNode
class ListNode(object):
def __init__(self, val, next=None):
self.val = val
self.next = next
"""
class Solution:
"""
@param head: The first node of the linked list.
@return: You should return the head of the reversed linked list.
Reverse it in-place.
"""
def reverse(self, head):
# write your code here
prev = None
while head:
tmp = head.next
head.next = prev
prev = head
head = tmp
return prev