Leetcode 206. Reverse Linked List

Leetcode 206. Reverse Linked List

包含迴圈和遞迴寫法

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

class Solution1 {
   public:
    ListNode* reverseList(ListNode* head) {
        if(!head || !head->next)
            return head;
        ListNode* future = head->next, *copy = nullptr, *prev = nullptr;
        do {
            copy = future->next;
            future->next = head;
			head->next = prev;
			prev = head;
            head = future;
            future = copy;
        } while(copy);
        return head;
    }
};