递归地翻转一个链表

手法非常巧妙，值得细细品味。

struct ListNode {int val;ListNode *next;ListNode(int x) : val(x), next(NULL) {}};ListNode *reverseList(ListNode *head) {if (head == NULL || head->next == NULL)return head;ListNode *head_next = head->next;ListNode *ret = reverseList(head->next);head_next->next = head;head->next = NULL;return ret;}