使用“原始”指针的问题。如何从自定义链表中删除重复值？

struct ListNode {
    int val;
    ListNode* next;
    ListNode(int x) : val(x), next(nullptr) {}
};

void removeDuplicates(ListNode* head) {
    if (!head) return;

    ListNode* current = head;
    while (current) {
        ListNode* runner = current;
        while (runner->next) {
            if (runner->next->val == current->val) {
                ListNode* temp = runner->next;
                runner->next = runner->next->next;
                delete temp; // 释放内存
            } else {
                runner = runner->next;
            }
        }
        current = current->next;
    }
}