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Coderust: Hacking the Coding Interview

Reverse Even Nodes in a Linked List

Explore how to reverse the nodes at even positions in a singly linked list without extra memory allocation. Understand the process of separating even and odd nodes, reversing the even nodes by pushing them to a new list's head, and merging them back alternately. This lesson guides you to implement an efficient O(n) time and space solution, enhancing your linked list manipulation skills for coding interviews.

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Statement

Given a singly linked list, reverse the nodes at even positions and return the linked list.

Example

Let’s take the below linked list as an example:

g head1 head a 7 head1->a NULL NULL b 14 a->b c 21 b->c d 28 c->d e 9 d->e e->NULL

After reversing the nodes at even positions, it should look like this:

g head1 head a 7 head1->a NULL NULL d 28 a->d b 14 e 9 b->e c 21 c->b d->c e->NULL

Sample input

[7, 14, 21, 28, 9]

Expected output

[7, 28, 21, 14, 9]

Try it yourself

Files
main.cpp
LinkedList.cpp
LinkedListNode.cpp
#include <vector>
#include "LinkedList.cpp"
using namespace std;
typedef LinkedListNode* NodePtr;
NodePtr ReverseEvenNodes(NodePtr head) {
	//TODO: Write - Your - Code
	return head;
}
...