leetcode/206_gp.cpp at dev · xcheng85/leetcode · GitHub

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */

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

        ListNode* node = reverseList(head -> next);

        head -> next->next = head;
        head -> next = NULL;

        return node;
    }
};


ListNode* reverseList(ListNode* head) {
        ListNode* pre=NULL;
        ListNode* next=NULL;
        while(head!=NULL){
            next=head->next;
            head->next=pre;
            pre=head;
            head=next;
        }
        return pre;
    }