链接：http://leetcode.com/onlinejudge

Add Two Numbers

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

思路：链表的操作，逐位相加并加上可能需要进位的数

/**

 * Definition for singly-linked list.

 * public class ListNode {

 *     int val;

 *     ListNode next;

 *     ListNode(int x) {

 *         val = x;

 *         next = null;

 *     }

 * }

 */

public class Solution {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        int sum=0,append=0,left=0;

        ListNode root=new ListNode(0);

		ListNode result=root;

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

			int v1=l1!=null?l1.val:0;

			int v2=l2!=null?l2.val:0;

			sum=v1+v2+append;

			append=sum/10;

			left  =sum%10;

			ListNode cursor=new ListNode(left);

			result.next=cursor;

			result=cursor;

			if(l1!=null)

				l1=l1.next;

			if(l2!=null)

				l2=l2.next;

		}

		if(append>0){

			ListNode cursor=new ListNode(append);

			result.next=cursor;

		}

		return root.next;

    }

}