leetcode 2. Add Two Numbers | 2. 两数相加（Java）

水深无声 2022-08-30 11:46 42阅读 0赞

## 题目 ##

[https://leetcode.com/problems/sum-of-two-integers/][https_leetcode.com_problems_sum-of-two-integers]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

需要注意 **当两个链表不一样长时** 的收尾处理。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_1_color_FFFFFF_t_70]

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */
    class Solution { 
        public ListNode addTwoNumbers(ListNode l1, ListNode l2) { 
            ListNode head = new ListNode();
            ListNode pre = head;
            short carry = 0;
            while (l1 != null || l2 != null) { 
                ListNode node;
                int a1 = 0;
                int a2 = 0;
                if (l1 != null) { 
                    a1 = l1.val;
                    l1 = l1.next;
                }
                if (l2 != null) { 
                    a2 = l2.val;
                    l2 = l2.next;
                }
                int sum = a1 + a2 + carry;
                if (sum >= 10) { 
                    node = new ListNode(sum % 10);
                    carry = 1;
                } else { 
                    node = new ListNode(sum);
                    carry = 0;
                }
                pre.next = node;
                pre = node;
            }
            if (carry == 1) { 
                pre.next = new ListNode(1);
            }
            return head.next;
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

[https_leetcode.com_problems_sum-of-two-integers]: https://leetcode.com/problems/sum-of-two-integers/
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20220829/4fd3646a0871478ea2db05ff19cb3b5e.png