解法：创建链表虚拟头节点很重要

/**
 * 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 
     * @param val int整型 
     * @return ListNode类
     */
    ListNode* deleteNode(ListNode* head, int val) {
        if (head == nullptr)    return nullptr;
        ListNode* dummyHead = new ListNode(0);
        dummyHead->next = head;
        ListNode* pCur = dummyHead;
        
        while (pCur->next) {
            if (pCur->next->val == val) {
                pCur->next = pCur->next->next;
            }
            else {
                pCur = pCur->next;
            }
        }
        ListNode* res = dummyHead->next;
        delete dummyHead;
        return res;
    }
};