Plus One Linked List -- LeetCode

weixin_30716725

于 2016-08-27 13:03:00 发布

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CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/fenshen371/p/5812850.html

本文介绍了一种使用递归方法解决链表表示的非负整数加一的问题。通过递归遍历链表，从最低位开始逐位加一，并处理进位情况，最终返回加一后的链表。

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Given a non-negative number represented as a singly linked list of digits, plus one to the number.

The digits are stored such that the most significant digit is at the head of the list.

Example:

Input:
1->2->3

Output:
1->2->4

思路：递归。

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     int help(ListNode* head) {
12         if (head->next == NULL) head->val++;
13         else head->val += help(head->next);
14         if (head->val < 10) return 0;
15         head->val = 0;
16         return 1;
17     }
18     ListNode* plusOne(ListNode* head) {
19         int credit = help(head);
20         if (!credit) return head;
21         ListNode *res = new ListNode(1);
22         res->next = head;
23         return res;
24     }
25 };