Reverse Linked List_recursion.cpp

/**
 * 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);
    }
    
private:
    ListNode* reverse(ListNode* head)
    {
        if(!head || !head->next)return head;
        ListNode* tail = head->next;
        ListNode* newHead = reverse(head->next);
        tail->next = head;
        head->next = nullptr;
        return newHead;
    }
};