Reverse Linked List
Understand how to reverse a singly linked list by manipulating pointers directly in C++. This lesson guides you through an efficient in-place reversal technique, enabling you to transform the list and return the updated head without extra space.
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Statement
Given the head of a singly linked list, reverse the linked list and return its updated head.
Constraints:
Let n be the number of nodes in a linked list.
-
n -
Node.value
Examples
Understand the problem
Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:
What is the output if the following linked list is provided as input?
4 → 2 → 7 → 8 → 9 → 0 → 2
9 → 0 → 2 → 8 → 4 → 2 → 7
7 → 2 → 4 → 8 → 2 → 0 → 9
2 → 0 → 9 → 8 → 7 → 2 → 4
0 → 2 → 2 → 4 → 8 → 9
Figure it out!
We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.
Try it yourself
Implement your solution in the following coding playground.
// Definition for a Linked List node// class ListNode {// public:// int val;// ListNode* next;// // Constructor// ListNode(int val = 0, ListNode* next = nullptr);// };ListNode *Reverse(ListNode *head){// Replace this placeholder return statement with your codereturn head;}