两数相加

Add Tow Numbers

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:

1
2
3

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

题目大意

2 个非空的逆序链表, 低位开始相加, 结果也以逆序输出.

解题思路

两数相加主要需要处理 进位 的问题.

1 2	Input: (9 -> 9) + (1 -> ) OutPut: 0 -> 0 -> 1

定义好如下链表结构:

type ListNode struct {
    Val int         // 当前节点的值
    Next *ListNode  // Next指向下个节点的指针
}

初始化一个空链表用于存储结果, 同时赋值给游标, 按位循环相加, 并处理进位, 结束条件不能使用 l.Next != nil, 这样还要额外去处理进位问题, 直接使用 l != nil 进行结束判断.

代码

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    ret := &ListNode{}
    cur := ret
    carry := 0
    
    for l1 != nil || l2 != nil || carry > 0 {
        tmp := 0
        if l1 != nil {
            tmp += l1.Val
            l1 = l1.Next

        }
        if l2 != nil {
            tmp += l2.Val
            l2 = l2.Next
        }
        tmp += carry
        carry = tmp / 10
        cur.Next = &ListNode{Val:tmp%10}
        
        cur = cur.Next
        
        
    }
    
    return ret.Next
}

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