Reverse a Linked List – Python (Step-by-Step)

🔁 Reverse a Linked List – Python (Step-by-Step) Hi All, Today I solved a fundamental problem in Data Structures: Reverse a Linked List . 📌 Problem Statement Given the head of a singly linked list , reverse the list and return the new head. 🔍 Example Input: 1 -> 2 -> 3 -> 4 -> 5 Output: 5 -> 4 -> 3 -> 2 -> 1 💡 Approach 🔹 Iterative Method (Optimal) 👉 We reverse the links one by one using pointers. 🧠 Step-by-Step Logic We use three pointers: prev → previous node curr → current node next_node → next node Steps: Initialize: prev = None curr = head Traverse the list: Store next node Reverse link Move pointers forward 💻 Python Code class ListNode : def __init__ ( self , val = 0 ): self . val = val self . next = None def reverseList ( head ): prev = None curr = head while curr : next_node = curr . next # store next curr . next = prev # reverse link prev = curr # move prev curr = next_node # move curr return prev 🔍 Dry Run For: 1 -> 2 -> 3 Steps: Reverse 1 → None Reverse 2 → 1 Reverse 3 → 2 → 1