cpa_lab_5_3_13_(6)-B.cpp

#include <iostream>

using namespace std;

class Node
{
    public:
        Node(int val);
        int value;
        Node* next;
};

Node::Node(int val) : value(val), next(nullptr) { }

class List
{
    public:
        List();
        void push_back(int value);
        void push_front(int value);
        bool pop_front(int value);
        bool pop_back(int value);
        int size();
        int at(int index);
        void insert_at(int index, int value);
        void remove_at(int index);
    private:
        Node* head;
        Node* tail;
};

int List::size() {
	Node *t = head;
	int i = 0;
	while (t != nullptr) {
		t = t->next;
		++i;
	}
	return i;
}
List::List() : head(nullptr) { }

int List::at(int index)
{
	Node *t = head;
	int i = 0;
	while (i < index && t != nullptr) {
		t = t->next;
		++i;
	}
	return t->value;
}

void List::insert_at(int index, int value) {
	Node *t = head, *pre = nullptr;
	int i = 0;
	while (i < index && t != nullptr) {
		pre = t;
		t = t->next;
		++i;
	}
	Node *n = new Node(value);
	if (pre == nullptr) {
		n->next = head;
		head = n;
	}
	else {
		n->next = pre->next;
		pre->next = n;
	}
}

void List::remove_at(int index) {
	Node *t = head, *pre = nullptr;
	int i = 0;
	while (i < index && t != nullptr) {
		pre = t;
		t = t->next;
		++i;
	}
	if (pre == nullptr) {
		head = head->next;
	}
	else {
		pre->next = t->next;
	}
	delete t;
}

void List::push_front(int value)
{
	Node* new_head = new Node(value);
    new_head->next = head;

    if(head == nullptr)
        tail = new_head;

    head=new_head;
}
void List::push_back(int value)
{
	if(head != nullptr)
    {
        Node* new_tail = new Node(value);
        tail->next = new_tail;
        tail = new_tail;
    }
    else push_front(value);
}

bool List::pop_front(int value)
{
	Node *t = head, *prev = nullptr;

	while (t != nullptr) {
		if (t->value == value) {
			if (prev == nullptr) {
				prev = head;
				head = head->next;
				if (head->next == nullptr)
					tail = head;
				delete prev;
			}
			else
			{
				if (t->next == nullptr)
					tail = prev;
				prev->next = t->next;
				delete t;
			}
			return true;
		}
		else
		{
			prev = t;
			t = t->next;
		}
	}
	return false;
}

bool List::pop_back(int value) {
	Node *t = head, *pre = nullptr, *temp = nullptr;
	while (t->next != nullptr)
	{
		if (t->value == value)
		{
			temp = pre;
		}
		pre = t;
		t = t->next;
	}
	if (tail->value == value) {
		temp = pre;
		tail = pre;
	}

	if (temp != nullptr) {
		t = temp->next;
		temp->next = t->next;

		delete t;
		return true;
	}
	return false;

}

void printList(List list)
{
	for (int i = 0; i < list.size(); i++)
	{
		cout << "list[" << i << "] == " << list.at(i) << endl;
	}
}
int main()
{
	List list;

	list.push_front(1);
	list.push_front(2);
	list.push_front(3);
	list.push_front(4);
	printList(list);
	cout << endl;

	list.remove_at(2);
	printList(list);
	cout << endl;

	list.insert_at(1, 6);
	printList(list);

	return 0;
}