# 203. Remove Linked List Elements

## 1.問題

![](https://901207480-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LGKoChvN9am4__HCIRK%2F-LJONT7zNU2kupuTu3Jw%2F-LJOlS7SyhUPvJImWMrp%2F2018080801.jpg?alt=media\&token=80b6c436-facf-4500-97e3-142d11418e37)

## 2.想法

* 基本上可以判斷指標的next是不是為目標, 如果是則讓next = next->next

## 3.程式碼

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

## 4.Performance

![](https://901207480-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LGKoChvN9am4__HCIRK%2F-LJONT7zNU2kupuTu3Jw%2F-LJOlaL153UfhBl63uwa%2F2018080802.jpg?alt=media\&token=b9a9542e-8c2c-469b-b6c0-c94de900f1ac)