LC-206 - Reverse Linked List

Reverse a singly linked list.

• Difficulty: EASY

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Exmaples

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

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Follow Up

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

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Solutions

1. Use iteraitve way to add the node in front of the reversed list
   • Time complexity: $O(n)$
   • Space complexity: $O(1)$
2. Use recursive way to reverse each node in the linked list
   • Time complexity: $O(n)$
   • Space complexity: $O(n)$