Grokking the Coding Interview: Patterns for Coding Questions

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Solution: Reverse a LinkedList

Problem Statement

Given the head of a Singly LinkedList, reverse the LinkedList. Write a function to return the new head of the reversed LinkedList.

Constraints:

The number of nodes in the list is the range [0, 5000].
-5000 <= Node.val <= 5000

Solution

To reverse a LinkedList, we need to reverse one node at a time. We will start with a variable current which will initially point to the head of the LinkedList and a variable previous which will point to the previous node that we have processed; initially previous will point to null.

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