0002. Add Two Numbers

# 2. Add Two Numbers#

## 题目 #

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.
``````

## 题目大意 #

2 个逆序的链表，要求从低位开始相加，得出结果也逆序输出，返回值是逆序结果链表的头结点。

## 解题思路 #

``````
Input: (9 -> 9 -> 9 -> 9 -> 9) + (1 -> )
Output: 0 -> 0 -> 0 -> 0 -> 0 -> 1

``````

## 代码 #

``````
package leetcode

/**
* Definition for singly-linked list.
* type ListNode struct {
*     Val int
*     Next *ListNode
* }
*/

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
head := &ListNode{Val: 0}
n1, n2, carry, current := 0, 0, 0, head
for l1 != nil || l2 != nil || carry != 0 {
if l1 == nil {
n1 = 0
} else {
n1 = l1.Val
l1 = l1.Next
}
if l2 == nil {
n2 = 0
} else {
n2 = l2.Val
l2 = l2.Next
}
current.Next = &ListNode{Val: (n1 + n2 + carry) % 10}
current = current.Next
carry = (n1 + n2 + carry) / 10
}
return head.Next
}

``````

Apr 8, 2023
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