Solution.java

package _2;
// remove the line of `package xxx.xxx.xxx.xxx;` when you commit it

/**
 * @author relish
 * @since 2018/04/02
 */

/**
 * Definition for singly-linked list.
 * public class ListNode {
 * int val;
 * ListNode next;
 * ListNode(int x) { val = x; }
 * }
 */
class Solution {
 public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
 ListNode firstNode = null;
 ListNode prev = null;

 int co = 0;
 while (l1 != null || l2 != null) {
 int val1 = l1 == null ? 0 : l1.val;
 int val2 = l2 == null ? 0 : l2.val;

 int val = val1 + val2 + co;
 if (val >= 10) {
 val %= 10;
 co = 1;
 } else {
 co = 0;
 }
 if (firstNode == null) {
 firstNode = new ListNode(val);
 prev = firstNode;
 } else {
 ListNode newNode = new ListNode(val);
 prev.next = newNode;
 prev = newNode;
 }

 l1 = l1 == null ? null : l1.next;
 l2 = l2 == null ? null : l2.next;
 }
 if (co == 1) {
 prev.next = new ListNode(1);
 }
 return firstNode;
 }

 public static void main(String[] args) {
 ListNode l1 = new ListNode(2);
 l1.next = new ListNode(4);
 l1.next.next = new ListNode(3);

 ListNode l2 = new ListNode(5);
 l2.next = new ListNode(6);
 l2.next.next = new ListNode(4);

 ListNode listNode = new Solution().addTwoNumbers(l1, l2);
 while (listNode != null) {
 System.out.print(listNode.val + " ");
 listNode = listNode.next;
 }
 }
}

class ListNode {
 int val;
 ListNode next;

 ListNode(int x) {
 val = x;
 }
}