Remove all elements from a linked list of integers that have value val.
Example
Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5
Credits: Special thanks to @mithmatt for adding this problem and creating all test cases.
- 先处理头部，如果头部就是要删除的值，直接让头部指向下一个节点，并释放原来的头部
while (head && head->val == val) {
struct ListNode *q = p->next;
free(head);
head = q;
}- 处理非头部节点，此时无需更新头部，只需要遍历等于删除值的节点即可。为了便于删除操作，判断后一个节点，若后一个节点值为删除值，则只需要删除后一个节点即可，否则指向下一个节点
struct ListNode *p = head;
while (p) {
struct ListNode *q = p->next;
if (q && q->val == val) {
p->next = q->next;
free(q);
} else {
p = p->next;
}
}struct ListNode *removeElements(struct ListNode *head, int val)
{
struct ListNode *p =head;
while (p && p->val == val) {
struct ListNode *q = p->next;
free(p);
p = q;
head = q;
}
while (p) {
struct ListNode *q = p->next;
if (q && q->val == val) {
p->next = q->next;
free(q);
} else {
p = p->next;
}
}
return head;
}