Reverse Linked List.py

# https://leetcode.com/problems/reverse-linked-list/
# Hak Soo Kim
# 2/3/2022

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def reverseList(self, head):
        prev = None
        while (head):
            nextNode = head.next
            head.next = prev
            prev = head
            head = nextNode
        return prev
        """
        :type head: ListNode
        :rtype: ListNode
        """

# Given the head of a singly linked list, reverse the list, and return the reversed list.
#
# Example 1:
#
#
# Input: head = [1,2,3,4,5]
# Output: [5,4,3,2,1]
# Example 2:
#
#
# Input: head = [1,2]
# Output: [2,1]
# Example 3:
#
# Input: head = []
# Output: []
#
# Constraints:
#
# The number of nodes in the list is the range [0, 5000].
# -5000 <= Node.val <= 5000