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描述：
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
本来想法（最笨的想法）是把两个链表都读出来组成数字，反转相加，再将二者的和反转存到一个链表，经谷歌提点，本来两个链表就是从个位开始的，一位一位相加，进位在下个高位继续加。
public class Solution { public static ListNode addTwoNumbers(ListNode l1, ListNode l2) { ListNode head = new ListNode(0); // empty header; ListNode resCur = head; ListNode cursor1 = l1; ListNode cursor2 = l2; int remad=0; int m=0; while(cursor1!=null || cursor2!=null){ int sum=0; int val1=0; int val2=0; if(cursor1!=null){ val1=cursor1.val; } if(cursor2!=null){ val2=cursor2.val; } sum=val1+val2+remad; remad=sum/10; m=sum%10; resCur.next=new ListNode(m); resCur=resCur.next; if(cursor1!=null) cursor1=cursor1.next; if(cursor2!=null) cursor2=cursor2.next; } if(remad!=0) resCur.next=new ListNode(remad); return head.next; } public static void main(String[] args){ ListNode l1=new ListNode(5); l1.next=new ListNode(4); ListNode l2=new ListNode(5); l2.next=new ListNode(5); ListNode resNum=new ListNode(0); resNum=addTwoNumbers(l1,l2); while (resNum!=null){ System.out.print(resNum.val+"->"); resNum=resNum.next; } } }
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原文地址：http://www.cnblogs.com/duanqiong/p/4403570.html
