Skip to content
A bird sitting on a nest of eggs. GitHub Twitter

206. Reverse Linked List with Python

leetcode easy-problem

URL: LeetCode Problem

Problem Description

Given the head of a singly linked list, reverse the list, and return the reversed list.

Examples:

  • Example 1: Blogster
Input: head = [1,2,3,4,5]
Output: [5,4,3,2,1]

Constraints:

  • The number of nodes in the list is the range [0, 5000].
  • 5000 <= Node.val <= 5000

Answer

Complexity

  • Time complexity: O(n)

  • Space complexity: O(1)

Code 

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
        prev = None

        while head:
            next_node = head.next
            head.next = prev
            prev = head
            head = next_node

        return prev