Reverse_a_linked_list.cpp

/*
Problem Statement:
-----------------
Given a linked list of N nodes. The task is to reverse this list.

Example 1:
---------
Input:
LinkedList: 1->2->3->4->5->6
Output: 6 5 4 3 2 1
Explanation: After reversing the list, elements are 6->5->4->3->2->1.

Example 2:
---------
Input:
LinkedList: 2->7->8->9->10
Output: 10 9 8 7 2
Explanation: After reversing the list,
elements are 10->9->8->7->2.

Your Task: The task is to complete the function reverseList() with head reference as the only argument and should return new head after reversing the list.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).
*/

// Link --> https://practice.geeksforgeeks.org/problems/reverse-a-linked-list/1#
 
// Code:
struct Node
{
    int data;
    struct Node *next;
}

class Solution
{
    public:
    //Function to reverse a linked list.
    struct Node* reverseList(struct Node *head)
    {
        struct Node *prev , *cur , *next;
        cur = head;
        prev = next = NULL;
        while (cur != NULL) 
        {
            next = cur->next;
            cur->next = prev;
            prev = cur;
            cur = next;
        }
        head = prev;
        
        return head;
    }
    
};