LSI.cs

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 inceputul listei

        // Constructori

        // 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;
        }

        // Metoda de adaugare a unui nod la inceputul listei si nodul retine valoarea val
        public void AddBegin(int val)
        {
            Nod p = new Nod(val);
            p.leg = L;
            L = p;
        }

        // Adauga un nod cu informatia val pe pozitia k in lista
        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;
            }
            // Inserez dupa nodul q
            p = new Nod(val);
            p.leg = q.leg;
            q.leg = p;
        }

        // 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) // Sterg primul nod
            {
                p = L;
                L = L.leg;
                p = null;
                return;
            }
            // Ma pozitionez pe al k-1-lea nod
            for (p = L; k > 2; p = p.leg)
                k--;
            q = p.leg;
            p.leg = q.leg;
            q = null;
        }

        // Proprietate care numara cate noduri are lista
        public int Count
        {
            get
            {
                int cnt = 0;
                for (Nod p = L; p != null; p = p.leg)
                    cnt++;
                return cnt;
            }
        }

        // Indexatorul
        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;
            }
        }

        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;
        }

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

        public static LSI operator +(int val, LSI A)
        {
            LSI B = new LSI(val);
            for (int i = 1; i <= A.Count; i++)
                B.Add(A[i], i + 1);
            return B;
        }
    }
}

Nod.cs


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

namespace p23_LSI
{
    class Nod
    {
        public int info;
        public Nod leg;

        public Nod(int val)
        {
            info = val;
            leg = null;
        }
    }
}


Program.cs


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

namespace p23_LSI
{
    class Program
    {
        static void Main(string[] args)
        {
            LSI A = new LSI();
            for (int i = 20; i >= 1; i--)
                A.AddBegin(i * i);
            Console.WriteLine(A);

            LSI B = new LSI();
            for (int i = 10; i >= 0; i--)
                B.AddBegin(i);

            LSI C = A + B;
            Console.WriteLine(C);

            B = A + 444;
            Console.WriteLine(A);
            Console.WriteLine(B);

            B = 333 + B;
            Console.WriteLine(B);
        }
    }
}