题解 | #反转链表#

使用三个指针实现：

/*
struct ListNode {
	int val;
	struct ListNode *next;
	ListNode(int x) :
			val(x), next(NULL) {
	}
};*/
class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
        if(pHead == nullptr || pHead->next == nullptr) {
            return pHead;
        }
        ListNode *cur = pHead;//at leat 2 nodes.
        ListNode *head = pHead;
        ListNode *next = nullptr;
        while(cur->next != nullptr) {
            //1st step:
            next = cur->next;// 
            cur->next = cur->next->next;// pull cur->next;
            next->next = head; 
            head = next;
            //cout << head->val << endl;
        }
      
        return head;
    }
};