反轉鏈表（LeetCode簡單篇206題）

反轉一個單鏈表

示例:
輸入: 1->2->3->4->5->NULL
輸出: 5->4->3->2->1->NULL

struct ListNode* reverseList(struct ListNode* head)
{
	struct ListNode* cur = head;
	struct ListNode* prev = NULL;
	struct ListNode* next;
	while(cur)
	{
	    //先獲取下一個結點
		next = cur->next;
		//更改當前結點的指向
		cur->next = prev;
		prev = cur;
		cur = next;
	}
	retur prev;
}