Untitled

/*Problem Statement : Reverse Linked List II
Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right, and return the reversed list.*/


/**
 * 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* Reverse(ListNode *head,ListNode *prev){
        ListNode* curr = head,*next;

        while(curr != nullptr){
            next = curr->next;
            curr->next = prev;

            prev =curr;
            curr = next;
        }

        return prev;

    }
    ListNode* reverseBetween(ListNode* head, int left, int right) {
        ListNode *left_l = head;
        ListNode* left_1 = head;
        
        for (int i = 1;i!=left;i++){
            left_l =left_l->next;
        }

        for (int i = 1; i!= left-1;i++){
            left_1 = left_1->next;
        }
        
        ListNode *right_r = left_l;
        ListNode *right_1 = left_l;

        int pos = right - left;

        if (pos == 0){
            return head;
        }

        for (int i = left;i != right;i++){
            right_r = right_r->next;
        }

        for (int i = left; i != right+1;i++){
            right_1 = right_1->next;
        }

        ListNode *head_l = Reverse(left_l,right_1);

        left_1->next = head_l;

        return head;



    }
};