leetcode 203.移除链表元素

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        if(head==NULL){
            return head;
        }
        if(head->next==NULL){
            if(head->val!=val){
                return head;
            }else{
                return NULL;
            }
        }
        ListNode* p=head->next;
        ListNode* q=head;
        ListNode* s;
        while(p->next!=NULL){
            if(p->val==val){
                s=p;
                p=p->next;
                q->next=p;
                delete(s);
            }else{
                p=p->next;
                q=q->next;
            }
        }
        if(p->val==val){
            delete(p);
            q->next=NULL;
        }

        if(head->val==val){
            if(head->next!=NULL){
                s=head;
                head=head->next;
            }else{
                return NULL;
            }
        }
        return head;
    }
};

最简单直白的写法