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) {
        // write code here
        if (head == nullptr || head->next == nullptr) {
            return head;
        }

        struct ListNode* pre = head;
        struct ListNode* node = head->next;

        while (pre -> next) {
            if (pre->val == node->val ) {
                pre->next = node->next;
                node = node->next;
            } else {
                pre = node;
                node = pre->next;
            }
        }

        return head;
    }
};