BM1 题解 | #反转链表#

/*
struct ListNode {
	int val;
	struct ListNode *next;
	ListNode(int x) :
			val(x), next(NULL) {
	}
};*/
class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
		if (pHead == nullptr) {
			return nullptr;
		}
		ListNode* pre = pHead;
		ListNode* cur = pHead->next;
		if (cur == nullptr) {
			return pHead;
		}
		ListNode* r = cur->next;
		cur->next = pre;
		pre->next = nullptr;
		ListNode* x;
		while (r != nullptr) {
			x = r->next;
			pre = cur;
			cur = r;
			r->next = pre;
			r = x;
		}
		return cur;
    }
};