206. Reverse Linked List

Reverse a singly linked list.

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None


class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if(head==None) or (head.next==None): return head;
        p=self.reverseList(head.next)
        head.next.next=head
        head.next=None
        return p