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Queue.h
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Queue.h
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#pragma once
template<class T>
class Queue
{
private:
struct Elem {
Elem* next = nullptr;
Elem* prev = nullptr;
T data = nullptr;
};
Elem* first = new Elem;
Elem* last = first;
public:
// Construct queue with one given element
Queue(T data) {
first->data = data;
}
~Queue() {
clear();
}
void clear() {
while (!empty()) {
pop();
}
}
// Push back new element
void push(T data) {
Elem* new_last = new Elem;
new_last->data = data;
if (first != nullptr) {
new_last->prev = last;
last->next = new_last;
}
else { // If queue was empty
first = new_last;
}
last = new_last;
}
// Pop front element
T pop() {
if (empty()) {
throw std::out_of_range("Queue is empty");
}
T data = first->data;
if (first->next != nullptr) {
first = first->next;
delete first->prev;
first->prev = nullptr;
}
else { // If queue turns empty
delete first, last;
first = nullptr;
last = nullptr;
}
return data;
}
bool empty() {
return (first == nullptr);
}
};