链表相加-

 思路：创建一个ReverseList方法，然后将开头每个值相加，当和超过十时则进一，并加到链表下一个数上，最后将生成的链表进行反转；

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */



public class Solution {
    /**
     *
     * @param head1 ListNode类
     * @param head2 ListNode类
     * @return ListNode类
     */
    public ListNode ReverseList(ListNode pHead){
        if(pHead == null){
            return null;
        }
        ListNode cur = pHead;
        ListNode pre = null;
        while(cur != null){
            ListNode temp = cur.next;
            cur.next = pre;
            pre = cur;
            cur = temp;
        }
        return pre;
    }
    public ListNode addInList (ListNode head1, ListNode head2) {
        if(head1 == null){
            return head2;
        }
        if(head2 == null){
            return head1;
        }
        head1 = ReverseList(head1);
        head2 = ReverseList(head2);
        ListNode res = new ListNode(-1);
        ListNode head = res;
        int carry = 0;
        while(head1 != null || head2 != null || carry != 0){
            int k1 = head1 == null ? 0 : head1.val;
            int k2 = head2 == null ? 0 : head2.val;
            int temp = k1 + k2 + carry;
            carry = temp / 10;
            temp %= 10;
            head.next = new ListNode(temp);
            head = head.next;
            if(head1 != null){
                head1 = head1.next;
            }
            if(head2 != null){
                head2 = head2.next;
            }
        }
        return ReverseList(res.next);
    }
}