using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WpfApplication2
{
    class List
    {
        private ListElem first;
        private ListElem curent;
        public void addToStart(float Value)
        {
            if (first == null)
            {
                first = new ListElem();
                first.data = Value;
            }
            else
                if (first != null)
                {
                    curent = new ListElem();
                    curent.data = Value;
                    curent.nextElement = first;
                    first = curent;
                }
        }
        public void deleteFirst()
        {
            if (first != null)
            {
                first = first.nextElement;
            }
            
        }
        public void addElementTo(float value, int position)
        {
            if (position == 0)
                addToStart(value);
            else
            {
                curent = first;
                for (int i = 0; i < position - 1; i++)
                {
                    curent = curent.nextElement;
                    if (curent == null)
                        return;
                }
                curent.nextElement = new ListElem(value, curent.nextElement);
            }
        }
        public void delAt(int position)
        {
          
            if (position == 0)
                deleteFirst();
            else
            {
                curent = first;
                for (int i = 0; i < position - 1; i++)
                {
                    curent = curent.nextElement;
                    if (curent == null)
                        return;
                }
                curent.nextElement = curent.nextElement.nextElement;
            }
        }
        public void DelAtEnd()
        {
            if (first == null)
                return;
            if (first.nextElement == null)
            {
                deleteFirst();
                return;
            }
            curent = first;
            while (curent.nextElement.nextElement != null)
            {
                curent = curent.nextElement;
            }
            curent.nextElement = null;
        }
        public void AddToEnd(float value)
        {
            if (first == null)
                addToStart(value);
            else
            {
                curent = first;
                while (curent.nextElement != null)
                {
                    curent = curent.nextElement;
                }
                curent.nextElement = new ListElem();
                curent.nextElement.data = value;
            }
        }
        public string ShowAll()
        {
            string s="";
            curent = first;
            while (curent != null)
            {
               s += curent.data.ToString("g") + " ";
                curent = curent.nextElement;
            }
            return s;
        }
        public void sort()
        {
            List pos = new List();
            List neg = new List();
            ListElem thisCurent = first;
            while(thisCurent!=null)
            {
                if (thisCurent.data > 0)
                    pos.AddToEnd(thisCurent.data);
                else
                    neg.AddToEnd(thisCurent.data);
                thisCurent = thisCurent.nextElement;
            }
            thisCurent = pos.first;
            while (thisCurent.nextElement != null)
                thisCurent = thisCurent.nextElement;
            first = pos.first;
            thisCurent.nextElement = neg.first;

        }
    }
    class ListElem
    {
        public float data;
        public ListElem nextElement = null;
        public ListElem() { }
        public ListElem(float data, ListElem next)
        {
            this.data = data;
            nextElement = next;
        }
    }
}