using System;

using System.Linq;

using System.Threading.Tasks;

using System.Collections.Generic;

using System.Collections.Concurrent;

using System.Threading;

​

public class Program

{

    //1

    private static String location;

    private static DateTime time;

    //2

    private static string result;

    //3

    private delegate void Printer();

    public static async Task Main()

    {

        //С#

        //1.1

        //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

        //One();

        static void One()

        {

            int[] arr = new int[2];

            arr[1] = 10;

            Object o = arr;

            int[] arr1 = (int[])o;

            arr1[1] = 100;

            Console.WriteLine(arr[1]);

            ((int[])o)[1] = 1000;

            Console.WriteLine(arr[1]);

        }

​

        //1.2

        //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

        /*

        int[] arr = new int[10];

        Two(arr);

        Console.WriteLine(arr.Length);

        */

        static void Two(int[] a)

        {

            int[] b = new int[5];

            a = b;

        }

​

        //1.3

        /*

        try 

        {

             Console.WriteLine("Exception:" + " " + 1/Convert.ToInt32(0));

        }

        finally

        {

             Console.WriteLine("Divide by Zero error");         

        }

        */

        //2.1

        //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

        //Console.WriteLine(location == null ? "location is null" : location);

        //Console.WriteLine(time == null ? "time is null" : time.ToString());

        //2.2

        //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

        //что-то изменится если мы изменим вызов await Task.Delay на Thread.Sleep?

        //SaySomething();

        //Console.WriteLine(result);

        static async Task<string> SaySomething()

        {

            await Task.Delay(5);

            result = "Hello world!";

            return "Something";

        }

​

        //2.3

        //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

        //UseDelegate();

        static void UseDelegate()

        {

            List<Printer> printers = new List<Printer>();

            int i = 0;

            for (; i < 10; i++)

            {

                printers.Add(() => Console.WriteLine(i));

            }

​

            foreach (var printer in printers)

            {

                printer();

            }

        }

    //2.4

    //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

    //TestStatic t = new TestStatic();

    //t.Print();

    //2.5

    //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

    //classA a = new classC();

    //Console.WriteLine(a.Print());

    //2.6

    //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

    //Derived d = new Derived();

    //int i = 10;

    //d.Func(i);

    //3.1

    await ONE();

    //3.2

    //await TWO();

    }

​

    //2.4

    //2.4

    //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

    //TestStatic t = new TestStatic();

    //t.Print();

    public class TestStatic

    {

        public static int TestValue;

        public TestStatic()

        {

            if (TestValue == 0)

            {

                TestValue = 5;

            }

        }

​

        static TestStatic()

        {

            if (TestValue == 0)

            {

                TestValue = 10;

            }

        }

​

        public void Print()

        {

            if (TestValue == 5)

            {

                TestValue = 6;

            }

​

            Console.WriteLine("TestValue : " + TestValue);

        }

    }

​

    //2.5

    //2.5

    //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

    //classA a = new classC();

    //Console.WriteLine(a.Print());

    public class classA

    {

        public virtual string Print()

        {

            return "classA";

        }

    }

​

    public class classB : classA

    {

        public override string Print()

        {

            return "classB";

        }

    }

​

    public class classC : classB

    {

        public new string Print()

        {

            return "ClassC";

        }

    }

​

    //2.6

    //2.6

    //КАКОЙ БУДЕТ ВЫВОД В КОНСОЛИ?

    // Derived d = new Derived();

    // int i = 10;

    // d.Func(i);

    public class Base

    {

        public virtual void Func(int x)

        {

            Console.WriteLine("Base.Func(int)");

        }

    }

​

    public class Derived : Base

    {

        public override void Func(int x)

        {

            Console.WriteLine("Derived.Func(int)");

        }

​

        public void Func(object o)

        {

            Console.WriteLine("Derived.Func(object)");

        }

    }

​

    //3.1

    private static async Task ONE()

    {

        var enumerable1 = Enumerable.Range(0, 10).Select(GetRes1);

        Console.WriteLine($"enumerable1 is : {enumerable1.GetType()}");

        var res1 = await Task.WhenAll(enumerable1);

        Print(res1);

        var asyncEnumerable1 = AsyncEnumerable.Range(0, 10).SelectAwait(async i => await GetRes1(i));

        Console.WriteLine($"asyncEnumerable1 is : {asyncEnumerable1.GetType()}");

        var res3 = await asyncEnumerable1.ToArrayAsync();

        Print(res3);

        static Task<int> GetRes1(int i) => Task.FromResult(i * i);

        static void Print(IEnumerable<int> numbers)

        {

            Console.WriteLine("Print");

            Console.WriteLine(string.Join(", ", numbers));

            Console.WriteLine("");

        }

    }

​

    //3.2

    private static async Task TWO()

    {

        var randomizer = new Random();

        var users = Enumerable.Range(1, 5).Select(x => new { token = $"user{randomizer.Next(1, 10)}" });

        var bag = new ConcurrentBag<object>();

        Parallel.ForEach(users, async item =>

        {

            // some pre stuff

            var response = await GetData(item);

            bag.Add(response);

        // some post stuff

        });

        Console.WriteLine(bag.Count);

        async Task<object> GetData(object userToken)

        {

            await Task.Delay(randomizer.Next(500, 1000));

            return Task.FromResult(userToken);

        }

    }

}/*

1 ВОПРОС

​

```

+-------------+---------+

| Column Name | Type    |

+-------------+---------+

| id          | int     |

| email       | varchar |

+-------------+---------+

id is the primary key column for this table.

Each row of this table contains an email. The emails will not contain uppercase letters.

```

​

Напишите запрос SQL, возращающий дубликаты email, поле email not null.

​

​

​

**Example 1:**

​

```

Input:

Person table:

+----+---------+

| id | email   |

+----+---------+

| 1  | a@b.com |

| 2  | c@d.com |

| 3  | a@b.com |

+----+---------+

Output:

+---------+

| Email   |

+---------+

| a@b.com |

+---------+

Explanation: a@b.com is repeated two times.

```

​

​

​

​

​

​

​

**2** **Question**:

​

Table: `Employee`

​

```

+-------------+---------+

| Column Name | Type    |

+-------------+---------+

| id          | int     |

| name        | varchar |

| salary      | int     |

| managerId   | int     |

+-------------+---------+

id is the primary key column for this table.

Each row of this table indicates the ID of an employee, their name, salary, and the ID of their manager.

​

```

​

​

Напишите SQL-запрос, возвращающий выборку сотрудников, которые зарабатывают больше, чем их менеджеры.

​

​

​

**Example 1:**

​

```

Input:

Employee table:

+----+-------+--------+-----------+

| id | name  | salary | managerId |

+----+-------+--------+-----------+

| 1  | Joe   | 70000  | 3         |

| 2  | Henry | 80000  | 4         |

| 3  | Sam   | 60000  | Null      |

| 4  | Max   | 90000  | Null      |

+----+-------+--------+-----------+

Output:

+----------+

| Employee |

+----------+

| Joe      |

+----------+

Explanation: Joe is the only employee who earns more than his manager.

```

​

​

​

​

​

​

​

**3** **Question**:

​

Table: `Salary`

​

```

+-------------+----------+

| Column Name | Type     |

+-------------+----------+

| id          | int      |

| name        | varchar  |

| sex         | ENUM     |

| salary      | int      |

+-------------+----------+

id is the primary key for this table.

The sex column is ENUM value of type ('m', 'f').

The table contains information about an employee.

​

```

​

Напишите запрос, чтобы поменять местами все значения `'f'` и `'m'` (т. е. изменить все значения `'f'` на `'m'` и наоборот) с помощью одного оператора update и без промежуточных таблиц

​

​

**Example 1:**

​

```

Input:

Salary table:

+----+------+-----+--------+

| id | name | sex | salary |

+----+------+-----+--------+

| 1  | A    | m   | 2500   |

| 2  | B    | f   | 1500   |

| 3  | C    | m   | 5500   |

| 4  | D    | f   | 500    |

+----+------+-----+--------+

Output:

+----+------+-----+--------+

| id | name | sex | salary |

+----+------+-----+--------+

| 1  | A    | f   | 2500   |

| 2  | B    | m   | 1500   |

| 3  | C    | f   | 5500   |

| 4  | D    | m   | 500    |

+----+------+-----+--------+

Explanation:

(1, A) and (3, C) were changed from 'm' to 'f'.

(2, B) and (4, D) were changed from 'f' to 'm'.

```

​

​

*/

​