206. Reverse Linked List

Edited by Charles

Easy · Python · LinkedList

Problem

Read the original problem on LeetCode.

The official page contains the problem statement, examples, and constraints.

Explanation, examples & other approaches

Core idea

Main logic:

Define two pointers: previous and current. Current points to the head and previous points to None.

Original study notes follow, including intermediate snippets and earlier attempts.

Main logic:

1. Define two pointers: previous and current.
2. Current points to the head and previous points to None.
3. Iterate the whole linked list:
   1. define temp to save current.next, since we need current to move forward after making the current node point to the previous.
   2. let current.next be previous (reversion is done)
   3. let previous be current (move both previous and current)
   4. let current be temp

Study record

Field	Value
Attempts	3
Mastery	❚❚❚
The Latest Attempt	January 4, 2026

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: Optional[ListNode]) -> Optional[ListNode]:
        current = head
        previous = None
        while current:
            temp = current.next
            current.next = previous
            previous = current
            current = temp

        return previous

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