[LeetCode] 206. Reverse Linked List

Reverse a singly linked list.

Hint:

A linked list can be reversed either iteratively or recursively. Could you implement both?

// 非递归版
class Solution {
public:
ListNode* reverseList(ListNode* head) {
ListNode *prev = nullptr, *cur;

while (head) {
cur = head;
head = head->next;
cur->next = prev;
prev = cur;
}

return prev;
}
};

class Solution {
public:
ListNode* reverseList(ListNode* head) {
if (head == nullptr || head->next == nullptr)
return head;

ListNode *revhead = reverseList(head->next);
head->next->next = head;
head->next = nullptr;

return revhead;
}
};