题目

给你两个非空链表来代表两个非负整数。数字最高位位于链表开始位置。它们的每个节点只存储一位数字。将这两数相加会返回一个新的链表。

示例：

输入：(7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4) 输出：7 -> 8 -> 0 -> 7

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34

/**
 * 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) {
        ListNode result = null;
        Deque<Integer> s1 = new LinkedList<>();
        Deque<Integer> s2 = new LinkedList<>();
        while (l1 != null) {
            s1.push(l1.val);
            l1 = l1.next;
        }
        while (l2 != null) {
            s2.push(l2.val);
            l2 = l2.next;
        }
        int carry = 0;
        while (!s1.isEmpty() || !s2.isEmpty() || carry > 0){
            int sum = carry;
            sum += s1.isEmpty()?0:s1.pop();
            sum += s2.isEmpty()?0:s2.pop();
            carry = sum / 10;
            ListNode node = new ListNode(sum % 10);
            node.next = result;
            result = node;
        }
        return result;
    }
}