//list

//todo: size, remove

#include "stdafx.h"

#include<iostream>

using namespace std;

struct ListNode

{

int value;

ListNode* next;

ListNode(int x) : value(x), next(NULL) {}

};

struct List

{

friend void print(ostream& os, List* L);

public:

List() : head(new ListNode(0)), tail(NULL) {}

~List();

void insertHead(int x);

void insertTail(int x);

private:

ListNode* head;

ListNode* tail;

};

void List::insertHead(int x)

{

ListNode* newp = new ListNode(x);

newp->next = head->next;

head->next = newp;

if (tail == NULL)

tail = newp;

}

List::~List()

{

ListNode* tmp = head->next;

if (tmp != NULL)

{

ListNode* t = tmp->next;

delete tmp;

tmp = t;

}

delete head;

}

void print(ostream& os, List* L)

{

if (L->head->next == NULL)

{

os << "the list is empty" << endl;

}

ListNode* tmp = L->head->next;

while (tmp != NULL)

{

os << tmp->value << " ";

tmp = tmp->next;

}

os << endl;

}

void List::insertTail(int x)

{

ListNode* newp = new ListNode(x);

if (tail == NULL)

{

tail = newp;

head->next = newp;

return;

}

tail->next = newp;

tail = newp;

if (head->next == NULL)

head->next = tail;

}

int main(int argc, char* argv)

{

List *L = new List();

L->insertTail(4);

L->insertHead(1);

L->insertHead(2);

L->insertHead(3);

L->insertTail(4);

L->insertTail(5);

L->insertHead(6);

print(cout, L);

delete L;

system("pause");

return 0;

}