Add Two Numbers Show result

You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored inreverse order, such that the 1's digit is at the head of the list. Write a function that adds the two numbers and returns the sum as a linked list.

Have you met this question in a real interview? 

Yes

Example

Given 7->1->6 + 5->9->2. That is, 617 + 295.

Return 2->1->9. That is 912.

Given 3->1->5 and 5->9->2, return 8->0->8.

/**

 * Definition for singly-linked list.

 * public class ListNode {

 *     int val;

 *     ListNode next;

 *     ListNode(int x) {

 *         val = x;

 *         next = null;      

 *     }

 * }

 */

public class Solution {

    /**

     * @param l1: the first list

     * @param l2: the second list

     * @return: the sum list of l1 and l2 

     */

    public ListNode addLists(ListNode l1, ListNode l2) {

        // write your code here

        ListNode head = new ListNode(0);

        ListNode node = head;

        int carry = 0;

        while(l1 != null && l2 != null){

            node.next = new ListNode((l1.val + l2.val + carry) % 10);

            carry = (l1.val + l2.val + carry) / 10;

            node = node.next;

            l1 = l1.next; l2 = l2.next;

            

        }

        

        if(l1 != null){

            while(l1 != null){

                node.next = new ListNode((l1.val + carry) % 10);

                carry = (l1.val + carry) / 10;

                l1 = l1.next;

                node = node.next;

            }

        }

        

        if(l2 != null){

            while(l2 != null){

                node.next = new ListNode((l2.val + carry) % 10);

                carry = (l2.val + carry) / 10;

                l2 = l2.next;

                node = node.next;

            }

        }

        

        

        if(carry != 0) node.next = new ListNode(carry);

        return head.next;

    }

}