每天一算：Remove Linked List Elements

 1// 203. Remove Linked List Elements
 2// https://leetcode.com/problems/remove-linked-list-elements/description/
 3// 使用虚拟头结点
 4// 时间复杂度: O(n)
 5// 空间复杂度: O(1)
 6class Solution {
 7public:
 8    ListNode* removeElements(ListNode* head, int val) {
 9
10        // 创建虚拟头结点
11        ListNode* dummyHead = new ListNode(0);
12        dummyHead->next = head;
13
14        ListNode* cur = dummyHead;
15        while(cur->next != NULL){
16            if(cur->next->val == val){
17                ListNode* delNode = cur->next;
18                cur->next = delNode->next;
19                delete delNode;
20            }
21            else
22                cur = cur->next;
23        }
24
25        ListNode* retNode = dummyHead->next;
26        delete dummyHead;
27
28        return retNode;
29    }
30};

1class Solution {
2public:
3    ListNode* removeElements(ListNode* head, int val) {
4        if (!head) return NULL;
5        head->next = removeElements(head->next, val);
6        return head->val == val ? head->next : head;
7    }
8};