LeetCode题解 —— 2. Add Two Numbers

墨蓝 2022-05-31 10:29 518阅读 0赞

## 题目内容： ##

Difficulty: **Medium**　Total Accepted: **442.7K**　Total Submissions: **1.6M**

> 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.  
>   
> **Example**  
> Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)  
> Output: 7 -> 0 -> 8  
> Explanation: 342 + 465 = 807.

### 题目描述 ###

读完题目和给出的例子，我们发现本题是将数字用链表进行倒序存储，342用链表存储表示为2 -> 4 -> 3，同样两个数加和的结果也是这样存储，这就有一个需要注意的地方，两个加数每位上的数字加和逢十进一的时候，结果链表中倒序存储，所以进位是向后的。

### 解题思路及代码实现(java) ###

public class Solution { 
        public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
            int carry =0;
    
            ListNode newHead = new ListNode(0);
            ListNode p1 = l1, p2 = l2, p3=newHead;
    
            while(p1 != null || p2 != null){
                if(p1 != null){
                    carry += p1.val;
                    p1 = p1.next;
                }
    
                if(p2 != null){
                    carry += p2.val;
                    p2 = p2.next;
                }
    
                p3.next = new ListNode(carry%10);
                p3 = p3.next;
                carry /= 10;
            }
    
            if(carry==1) 
                p3.next=new ListNode(1);
    
            return newHead.next;
        }
    }