Reverse Linked List

Problem: Reverse Linked List

We just record previous node so that we can reverse the whole list.

Code in Python:

class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        prev = None
        while head:
            head.next, prev, head = prev, head, head.next
        return prev