Leetcode 206. Reverse Linked List
文章作者：Tyan
博客：noahsnail.com | **** | 简书
1. Description
2. Solution
- Iteratively
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* reverseList(ListNode* head) {
ListNode* pre = nullptr;
ListNode* next = nullptr;
ListNode* current = head;
while(current) {
next = current->next;
current->next = pre;
pre = current;
current = next;
}
return pre;
}
};
- Recursively
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* reverseList(ListNode* head) {
return reverse(head, nullptr);
}
private:
ListNode* reverse(ListNode* current, ListNode* pre) {
if(!current) {
return nullptr;
}
ListNode* next = current->next;
if(next) {
current->next = pre;
return reverse(next, current);
}
current->next = pre;
return current;
}
};