利用二级指针删除链表内一个元素，传统的做法是：找到将要删除元素的前一个指针，然后再删除当前元素。代码示例：

void delete_node( elem_type x, struct node* l )
{
????struct node* p = find_prev ( x, l );

????if ( !p->next ) {
????????printf ( "element %d not in the struct node*\n", x );
????????return;
????}

????struct node* tmp = p->next;
????p->next = p->next->next;

????free ( tmp );
}

而通过二级指针的方法，则不需要如此。

void delete_version_2 ( struct node** head, elem_type x )
{
????for ( struct node** curr = head; *curr; ) {
????????struct node* entry = *curr;
????????if ( entry->elem == x ) {
????????????*curr = entry->next;
????????????free ( entry );
????????} else {
????????????curr = &entry->next;
????????}
????}
}