Reverse Linked List

Reverse Linked List.py

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

class Solution:
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        dummy = ListNode(0)
        while head:
            next = head.next
            head.next = dummy.next
            dummy.next = head
            head = next
        return dummy.next