题解 | #删除有序链表中重复的元素-I#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* deleteDuplicates(ListNode* head) {
        if (head == nullptr || head->next == nullptr) {
            return head;
        }
        ListNode *slow = head, *fast = head->next;
        while (fast) {
            if (slow->val == fast->val) {
                fast = fast->next;
            } else if (slow->next != fast) {
                slow->next = fast;
                fast = slow->next;
            } else {
                slow = slow->next;
                fast = slow->next;
            }
        }
        if (slow->next != fast) {
            slow->next = nullptr;
        }
        return head;
    }
};