#include <iostream>
using namespace std;

class Item {
public:
	Item(int val) {
		this->val = val;
		this->prev = NULL;
		this->next = NULL;
	}

	int val;
	Item* prev;
	Item* next;
};

class List {
private:
	Item* first;
	Item* last;
	int _size;
public:
	List() {
		first = NULL;
		last = NULL;
		_size = 0;
	}
	void push_back(int val) {
		_size++;
		if(last == NULL) {
			Item* i = new Item(val);
			first = i;
			last = i;
			return;
		}

		Item* i = new Item(val);
		last->next = i;
		i->prev = last;
		last = i;
	}
	Item* begin() {
		return first;
	}
	Item* end() {
		return last;
	}
	Item* find(int val) {
		for(Item* i = begin(); i != NULL; i = i->next) {
			if(i->val == val) {
				return i;
			}
		}
		return NULL;
	}
	bool erase(int pos) {
		if(pos >= size()){
			return false;
		}

		Item* i = begin();
		for(int counter = 1; counter <= pos; counter++) {
			i = i->next;
		}

        i->prev->next = i->next;
        i->next->prev = i->prev;

        delete i;
        _size--;
        return true;
	}
	int size() {
		return _size;
	}
	bool swap(int pos) {
		// swap pos with the next
		if(pos >= size()-1){
			return false;
		}

		Item* a = begin();
		for(int counter = 1; counter <= pos; counter++) {
			a = a->next;
		}
		Item* b = a->next;

		Item* before = a->prev;
		Item* after = b->next;

		if(before) {
			before->next = b;
		}
		else {
			first = b;
		}

		a->next = after;
		a->prev = b;
		b->next = a;
		b->prev = before;

		if(after) {
			after->prev = a;
		}
		else {
			last = a;
		}

		return true;
	}
};

void printList(List* v) {
	for(Item* i = v->begin(); i; i = i->next) {
		cout<<i->val<<" ";
	}
	cout<<endl;
}

void printListR(List* v) {
	for(Item* i = v->end(); i; i = i->prev) {
		cout<<i->val<<" ";
	}
	cout<<endl;
}

void test(List* v) {
	cout<<"Forward: ";
	printList(v);
	cout<<"Reverse: ";
	printListR(v);
}

int main() {
	List v;

	//test 1
	cout<<"- Test 1\n";
	v.push_back(10);
	v.push_back(8);
	v.push_back(37);
	v.push_back(1);
	v.push_back(0);
	v.push_back(5);
	test(&v);

	//test 2
	cout<<"- Test 2\n";
	Item* x = v.find(8);
	cout<<"Before: "<<x->prev->val<<" | Current: "<<x->val<<" | After: "<<x->next->val<<endl;

    //test 3
    cout<<"- Test 3\n";
    v.erase(3);
    test(&v);

    //test 4
    cout<<"- Test 4\n";
    v.swap(2);
    test(&v);

    //test 5
    cout<<"- Test 5\n";
    v.swap(3);
    test(&v);

	return 0;
}