leetcode#2-Add Two Numbers-java

题目：

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

解法：

public class AddTwoNumbers_2 {    public class ListNode {       int val;       ListNode next;       ListNode(int x) { val = x; }   }    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        int carry = 0;        ListNode l = new ListNode(0);        ListNode first = l;        while(l1!=null || l2!=null){            ListNode next = new ListNode(0);            int a = l1==null?0:l1.val;            int b = l2==null?0:l2.val;            next.val = (a+b+carry)%10;            l.next = next;            l = l.next;            carry = (a+b+carry)/10;            l1 = l1==null?null:l1.next;            l2 = l2==null?null:l2.next;        }        while (carry>0){            ListNode next = new ListNode(0);            next.val = carry%10;            carry = carry/10;            l.next = next;            l = l.next;        }        return first.next;    }}