Add Two Numbers

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 contain a single digit.
Add the two numbers and return it as a linked list.

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

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8



/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dum = new ListNode(-1), curt = null;
        int sum = 0, carry = 0;
        curt = dum;
        
        while(null != l1 || null != l2 || 0 != carry){
            sum = 0;
            
            if(null != l1){
                sum += l1.val;
                l1 = l1.next;
            }
            
            if(null != l2){
                sum += l2.val;
                l2 = l2.next;
            }
            
            sum += carry;
            carry = sum / 10;
            ListNode temp = new ListNode(sum % 10);
            curt.next = temp;
            curt = curt.next;
        }
        
        return dum.next;
    }
}