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

Machine Learning Projects

Table of Contents

Question

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

Example 1:

Machine Learning Projects
Input: head = [1,2,3,4,5]
Output: [5,4,3,2,1]

Example 2:

Machine Learning Projects
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

Follow up: A linked list can be reversed either iteratively or recursively. Could you implement both?

Python Solution

# 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: ListNode) -> ListNode:
        prev = None
        curr = head
        
        while curr:
            nex = curr.next
            curr.next = prev
            prev = curr
            curr = nex
        return prev

Leave a Comment

Your email address will not be published. Required fields are marked *