//check theo mssv, update phan tu tim thay theo s
        public void Update(SV s)
        {
            for (int i = 0; i < this.n; i++)
            {
                SV temp = this.arr[i];
                if (temp.MSSV == s.MSSV)
                {
                    temp.NameSV = s.NameSV;
                    temp.Age    = s.Age;

                    this.arr[i] = temp;
                }
            }
        }
        static void Main(string[] args)
        {
            SV sv1 = new SV
            {
                MSSV   = "102",
                NameSV = "TDD",
                Age    = 21,
            };

            SV sv2 = new SV
            {
                MSSV   = "103",
                NameSV = "BQK",
                Age    = 22,
            };

            SV sv3 = new SV
            {
                MSSV   = "104",
                NameSV = "NNQ",
                Age    = 23,
            };

            QLSV db = new QLSV();

            db.Add(sv1);
            db.Add(sv2);

            db.Insert(sv3, 1);
            db.ToString();

            Console.WriteLine("Index of SV2: " + db.IndexOf(sv2));

            Console.WriteLine("Removing sv3");
            db.Remove(sv3);
            db.ToString();

            Console.WriteLine("Updating sv2");
            SV sv4 = new SV
            {
                MSSV   = "103",
                NameSV = "Khoi Bui",
                Age    = 25,
            };

            db.Update(sv4);
            db.ToString();
        }
        //Delete sv in K
        public void RemoveAt(int k)
        {
            SV[] newarr = new SV[n - 1];
            int  idx    = 0;

            for (; idx < k; idx++)
            {
                newarr[idx] = this.arr[idx];
            }
            for (; idx < n - 1; idx++)
            {
                newarr[idx] = this.arr[idx + 1];
            }
            this.arr = newarr;
            this.n  -= 1;
        }
        //insert
        public void Insert(SV s, int k)
        {
            SV[] newarr = new SV[n + 1];
            int  idx    = 0;

            for (; idx < k; idx++)
            {
                newarr[idx] = this.arr[idx];
            }
            newarr[idx] = s;
            idx        += 1;
            for (; idx < n + 1; idx++)
            {
                newarr[idx] = this.arr[idx - 1];
            }
            this.arr = newarr;
            this.n  += 1;
        }
        //Find and delete
        public void Remove(SV s)
        {
            int idx = this.IndexOf(s);

            this.RemoveAt(idx);
        }
 //add vao cuoi mang
 public void Add(SV s)
 {
     this.Insert(s, n);
 }