题解 | #牛群排列去重#

/**
 * 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) {
        //ListNode* fakehead = new ListNode(0);
        //fakehead ->next = head;
        if(head == nullptr) return nullptr;
        ListNode* left = head;
        ListNode* right = head ->next;
        while(right && right ->next)
        {
            if(left ->val == right ->val) // 把所有重复的元素遍历完毕
            {
                while(right && left ->val == right ->val) //小心指针越界
                {
                    right = right ->next;
                }
                left ->next = right;
            }
            if(right == nullptr) break;
            left = left ->next;
            right = right ->next;
        }
        if(right && left ->val == right ->val) left ->next = right ->next;
        return head;
    }
};