text: /**
   * 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) {
          ListNode* prev = NULL;
          ListNode* curr = head;
          ListNode* temp = NULL;
          while(curr!=NULL)
          {
              temp=curr->next;
              curr->next = prev;
              prev = curr;
              curr = temp;
          }
          return prev;
      }
  };