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

namespace p23_LSI
{
    class LSI
    {
        Nod L; // referinta la liste

        //constructorul care construieste lista
        //cu un nod care retine valoarea val

        public LSI(int val)
        {
            L = new Nod(val);
        }

        public LSI()
        {
            L = null;
        }

        //Destructorul
        ~LSI()
        {
            L = null;
        }

        //Sterge al k-lea nod din lista
        public void Erase(int k)
        {
            Nod p, q;
            int n = Count;
            if (k <= 0 || k > n) return;
            if (k == 1)
            {
                p = L;
                L = L.leg;
                p = null;
                return;
            }
            //ma pozitionez pe al k-1 lea nod ca sa pot sterge nodul urmator
            for (p = L; k > 2; p = p.leg)
                k--;
            q = p.leg;
            p.leg = q.leg;
            q = null;
        }

        //indexator
        public int this[int i]
        {
            get
            {
                int n = Count;
                if (i <= 0) i = 1;
                if (i > n) i = n;
                Nod p;
                for (p = L; p != null && i > 1; p = p.leg)
                {
                    i--;
                }
                return p.info;
            }
            set
            {
                int n = Count;
                if (i <= 0) i = 1;
                if (i > n) i = n;
                Nod p;
                for (p = L; p != null && i > 1; p = p.leg)
                {
                    i--;
                }
                p.info = value;
            }
        }

        //adaugare a unui nod LA INCEPUTUL LISTEI
        public void AddBegin(int val)
        {
            Nod p = new Nod(val);
            p.leg = L;
            L = p;
        }

        public void Add(int val, int k)
        {
            int n = Count;
            if (k <= 1) //adauga la inceput in lista
            {
                AddBegin(val);
                return;
            }
            Nod p, q;
            q = L;
            for (p = L; p != null && k > 1; p = p.leg)
            {
                k--;
                q = p;
            }
            //inserare dupa nodul p
            p = new Nod(val);
            p.leg = q.leg;
            q.leg = p;
        }

        public int Count
        {
            get
            {
                int cnt = 0;
                for (Nod p = L; p!=null; p=p.leg)
                {
                    cnt++;
                }
                return cnt;
            }
        }

        public override string ToString()
        {
            string s = "";
            for (Nod p = L; p!=null; p=p.leg)
            {
                s += p.info + " ";
            }
            return s;
        }

        //redefinirea operatorilor
        public static LSI operator +(LSI A, LSI B)
        {
            LSI C = new LSI();
            Nod p;
            int k=0;
            for(p = A.L; p!=null; p = p.leg)
            {
                k++;
                C.Add(p.info, k);
            }
            for (p = B.L; p != null; p = p.leg)
            {
                k++;
                C.Add(p.info, k);
            }
            return C;
        }
    }
}