Add two numbers

addTwoNumbers.java

/*

You are given two linked lists representing two non-negative numbers. 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.

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) {
        int carry = 0;
        ListNode head = l1;
        ListNode tail = l1;
        while(l1 != null && l2!= null) {
            tail = l1;
            int newL1 = (l1.val + l2.val + carry) % 10;
            carry = (carry + l1.val + l2.val) / 10;
            l1.val = newL1;
            l1 = l1.next;
            l2 = l2.next;
        }
        
        if (carry == 0) {
            if (l2 != null) {
                tail.next = l2;
            } 
            return head;
        } else {
                if (l2 == null) {
                while(l1 != null & carry != 0) {
                    tail =l1;
                    int newL1 = (l1.val + carry) % 10;
                    carry = (l1.val + carry) / 10;
                    l1.val = newL1;
                    l1 = l1.next;
                }
            } else if (l1 == null) {
                tail.next = l2;
                while(l2 != null & carry != 0) {
                    tail = l2;
                    int newL1 = (l2.val + carry) % 10;
                    carry = (l2.val + carry) / 10;
                    l2.val = newL1;
                    l2 = l2.next;
                }
            }
            if(carry != 0) {
                tail.next = new ListNode(carry);
            }
        }
        
        return head;
    }
}