leetcode 203

struct ListNode* removeElements(struct ListNode* head, int val) 
{
    struct ListNode * tmp = (struct  ListNode *)malloc(sizeof(struct ListNode));
    struct ListNode * pre = tmp;
    pre->next = head;
    while(head != NULL)
    { 
        if(head->val == val) { 
            head= head->next;
            pre->next = head;
        }else{
            head = head->next;
            pre = pre->next;
        } 
    } 
    return tmp->next;
}

基本思路：

在删某个节点的时候需要修改该节点前面节点的next指针，所以需要有一个pre指针

另外需要有个节点来保存节点最初的位置 。

struct ListNode* removeElements(struct ListNode* head, int val)
{
    struct ListNode * tmp = (struct  ListNode *)malloc(sizeof(struct ListNode));
    struct ListNode * pre = tmp;
    pre->next = head;
    while(head != NULL)
    {
        if(head->val == val) {
            head= head->next;
            pre->next = head;
        }else{
            head = head->next;
            pre = pre->next;
        }
    }
    return tmp->next;
}