---
tags: data_structure_python
---

# Reverse Linked List <img src="https://img.shields.io/badge/-easy-brightgreen">

Reverse a singly linked list.

**Example:**

Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL

**Follow up:**

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

# Solution

### Solution 1: Iterative

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

class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        prev = None
        curr = head
        
        while curr != None:
            tmp = curr.next
            curr.next = prev
            prev = curr
            curr = tmp
        
        return prev

### Solution 2: Recursive

# Definition for singly-linked list.
class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None
        
class Solution:            
            
    def reverseList(self, head: ListNode) -> ListNode:
        if head == None or head.next == None:
            return head
        else:
            curr = self.reverseList(head.next)
            head.next.next = head
            head.next = None
            return curr