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#ifndef LINKED_LIST_H
#define LINKED_LIST_H
template <typename T>
struct llink {
llink<T>* before = nullptr;
llink<T>* after = nullptr;
T* value;
llink () { };
llink (T* val) : value(val) { }
~llink () { this->unlink(); }
void unlink ();
};
template <typename T>
struct llist {
llink<T>* head;
llink<T>* tail;
llink<T>* __cur;
T* cur() { return __cur->value; }
int length = 0;
llist ();
void push ( T* );
T& peek ();
T& pop ();
/*
* Adds two linked lists together.
* O(1) time.
* destroys new__ in the process, but keeps the elements.
* make sure to free(new__) after.
*/
void operator += (llist<T>& other);
int size () { return length; }
bool empty () { return length == 0; }
void reset ();
};
template <typename T>
llist<T>::llist () {
this->__cur = this->head = new llink<T>;
this->tail = new llink<T>;
head->after = tail;
tail->before = head;
}
#define FIRST(lst) (lst)->head->after
#define FIRST_V(lst) (lst)->head->after->value
#define LAST(lst) (lst)->tail->before
#define LAST_V(lst) (lst)->tail->before->value
template <typename T>
void llist<T>::push(T* val) {
auto l = new llink<T>(val);
l->after = FIRST(this);
FIRST(this) = l;
l->after->before = l;
l->before = this->head;
++this->length;
// TODO do I want to change that?
this->__cur = l;
}
template <typename T>
void llist<T>::reset () {
llink<T> *link = this->head, *next;
while (link != this->tail) {
next = link->after;
delete link;
link = next;
}
this->__cur = this->head;
}
template <typename T>
void llink<T>::unlink () {
if (this->before != nullptr) this->before->after = this->after;
if (this->after != nullptr) this->after->before = this->before;
}
template <typename T>
T& llist<T>::peek() {
if (this->empty()) return nullptr;
return FIRST(this)->value;
}
template <typename T>
T& llist<T>::pop() {
if (this->empty()) return nullptr;
llink<T>* frst = FIRST(this);
frst.unlinke();
T& retval = frst->value;
--this->length;
delete frst;
return retval;
}
template <typename T>
void llist<T>::operator+= (llist<T>& other) {
/* Link end of dest onto start of new__. */
LAST(this)->after = FIRST(other);
FIRST(other)->before = LAST(this);
/* Free the two now not needed end links. */
delete other->head;
delete other->tail;
/* Update dest with new__ tail ptr. */
this->tail = other->tail;
this->length += other->length;
}
// template <typename T>
// std::ostream& std::operator<<(std::ostream&, llist<T>);
#if 0
DEEP_COPY
LINK(TYPE)* n = FIRST(src);
while (n->after != NULL) {
NEW(TYPE, cpy);
DEEP_COPY(TYPE)(cpy, n->value);
PUSH(LLIST(TYPE)) ( dest, cpy );
n = n->after;
}
return 0;
#endif
/*
* Resets a linked list by removing all it's objects.
* FREE's all elements stored in the list.
*/
// int RESET(LLIST(TYPE)) ( LLIST(TYPE)* llist );
#if 0
LLIST(TYPE)* RESOLVE(LLIST(TYPE)) (LLIST(TYPE)* dest, LLIST(TYPE)* new_);
if (dest == NULL) return new__;
APPEND(LLIST(TYPE))(dest, new__);
return dest;
#endif
#endif /* LINKED_LIST_H */
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