2. Add Two Numbers

//Code By: Nikhil

/**
 * 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* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode *ans=new ListNode();
        ListNode *p=l1,*q=l2,*curr=ans;
        int carry=0;
        while(p!=NULL || q!=NULL){
            int x= (p!=NULL)? p->val:0;
            int y= (q!=NULL)? q->val:0;
            int sum = carry + x + y;
            carry = sum/10;
            curr->next = new ListNode(sum%10);
            curr = curr->next;
            if(p!=NULL)
                p=p->next;
            if(q!=NULL)
                q=q->next;
        }
        if(carry>0)
            curr->next = new ListNode(carry);
        return ans->next;
    }
};