leetcode 445两数相加 ii

/**
 * 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) {
        Stack<ListNode> s1=new Stack<>();
        Stack<ListNode> s2=new Stack<>();
        Stack<ListNode> result=new Stack<>();
        //入栈
        while(l1!=null)
        {
            s1.push(l1);
            l1=l1.next;
        }
        while(l2!=null)
        {
            s2.push(l2);
            l2=l2.next;
        }
        int carried = 0;
        while(!s1.isEmpty()||!s2.isEmpty())
        {
            int sum=carried;//进位，初始化
            if(!s1.empty())
            {
                sum+=s1.pop().val;
            }
            if(!s2.empty())
            {
                sum+=s2.pop().val;
            }
            carried=sum/10;
            sum%=10;
            result.push(new ListNode(sum));
        }
        //需要进位
        if(carried!=0)
        {
            result.push(new ListNode(carried));
        }
        ListNode node = new ListNode(-1);
        ListNode dummpy = node;
        while(!result.isEmpty())
        {
            node.next=result.pop();
            node = node.next;
        }
        return dummpy.next;
    }
}