• 递归法

ListNode* reverse(ListNode *pre,ListNode *cur){
        if(cur == NULL) return pre;
        ListNode *next = cur->next;
        cur->next = pre;
        return reverse(cur,next);
    }
    ListNode* reverseList(ListNode* head) {
        return reverse(NULL,head);
    }

• 迭代法

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