連結：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：連結串列的操作，逐位相加並加上可能需要進位的數

/**
 * 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;
	
    }
}