Add Two Numbers

 You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

 

Example 1:

Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.

Example 2:

Input: l1 = [0], l2 = [0]
Output: [0]

Example 3:

Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]

Solution

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode result = new ListNode(0);
        ListNode head = result;
        int carry=0;        
        while(l1!=null || l2!=null) {
            int sum = 0;
            if(l1 != null){
                sum = sum+l1.val;
                l1 = l1.next;
            }
            if(l2 != null) {
                sum = sum+l2.val;
                l2 = l2.next;
            }
            sum = sum +carry;
            result.next = new ListNode(sum%10);
            carry = sum/10;
            result = result.next;
        }
        if(carry>0)
            result.next = new ListNode(carry);
        }
        return head.next;
    }
}