Reverse Linked List.cpp

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
         
        // pointers that traverse through the linked list  
        ListNode *current=head, *next=NULL, *prev=NULL;
        
        //iterate through the list to reverse it
        while(current!=NULL)
        {
            next=current->next;
            current->next=prev;
            prev=current;
            current = next;
        }
        //assign head to the last element
        head = prev;
                
        //return the pointer that points to the middle element
        return head;
    }
};