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

同

调整顺序即可

/** * 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) {        String s1 = toStr(l1);        String s2 = toStr(l2);        return toNode(addTowStr(s1, s2));    }        private String toStr(ListNode node) {        StringBuilder sr = new StringBuilder();        if (node == null)            return sr.toString();        while (node != null) {            sr.append(node.val);            node = node.next;        }        return sr.toString();    }        private ListNode toNode(String str) {        if (str == null)            return null;                ListNode cur = new ListNode(str.charAt(0)-'0');        ListNode head = cur;        for (int i=1; i
     
       0)            ret.append(over);        return ret.toString();    }        }