203. Remove Linked List Elements

1.問題

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