Lesson # 2. Programming on c sharp, condition statements

To do: Request user to input an integer. Convert input to integer. Check to see if the number is positive or negative. Output the result (a phrase «positive» or «negative»).
 
Note: you can use one of the folowing ways to convert the variable:

1) int numb = Convert.ToInt32(Console.ReadLine());
2) int numb = Int32.Parse(Console.ReadLine());

Expected output:

Please enter an integer value and press Enter
50
The result: The entered number was positive

Please enter an integer value and press Enter
-7
The result: The entered number was negative

[Solution and Project name: Lesson_2Task1, file name L2Task1.cs]

To do: A two-digit integer is given (is entered). Output its right and left digits (operations %, /).
  
Note: the number -56 consists of digits 5 and 6, but not -5 and -6. To output an absolute value of the number:

...
// importing namespace with a class Math
using static System.Math;
...
Math.Abs(number);

  
Note: Don’t forget to convert the variable for the inputted number to integer type (Int32.Parse(...)).
 

Expected output:

Please enter a two-digit number:
50
The result: right digit is 0, left digit is 5

Please enter a two-digit number:
-76
The result: right digit is 6, left digit is 7

[Solution and Project name: Lesson_2Task2, file name L2Task2.cs]

To do: A three-digit number is given (is entered). Set its middle digit to a value of 0.
  
Note 1: First, you have to get the digits of the number. Then, set the middle digit to 0. Afterward you have to make a number of the digits. To make a number of three digits use the example:

if we have 1, 2, 3
1*100 + 2*10 + 3 = 123

  
Note 2: Don’t forget to convert the variable for the inputted number to integer type (Int32.Parse(...)).
 

Exected output:

Please enter a three-digit number:
523
The digits: 5,2,3; the resulting number: 503

[Solution and Project name: Lesson_2Task3, file name L2Task3.cs]

To do: Three integers are given (they are entered). Output true if any two of them are not equal, and false otherwise.
  
Note: Boolean operation check for inequality is != , logical And operation is &&, logical Or operation is ||:

if (a!=b || a!=c) {...}

Expected output:

Please enter three numbers:
13, -4, 6 
The result: true

Please enter three numbers:
6, -4, 6
The result: false

Please enter three numbers:
13, 13, 6 
The result: false

[Solution and Project name: Lesson_2task4, file name L2Task4.cs]

To do: Integers a, b and c are given (they are entered). Print True if a triangle with matching side lengths can exist, print False otherwise. If the triangle exists, print its area.

Note: Remember the «triangle inequality». To calculate the area, use Heron’s formula (p means half-perimeter):

Expected output:

Please enter three numbers:
4, 8, 6
The result: exists = true, area is 11.61895003

[Solution and Project name: Lesson_2task5, file name L2Task5.cs]

To do: Integer number x is entered. Calculate the value of the function f:

Note: The ∪ sign means boolean or ( || sign in C#):

// example:
(a<b)||(a<c)

Expected output:

Enter an integer: 
>>> 4
Result is 8

[Solution and Project name: Lesson_2task6, file name L2Task6.cs]

To do: Real number x is entered. Calculate the value of the function f:

Note: To calculate sin you should use Math class:

Math.Sin(x)

Expected output:

Enter a real: 
...

[Solution and Project name: Lesson_2task7, file name L2Task7.cs]

To do: Request user to input a serial number of the day of the week (1, 2, 3, …, 7). Check the input and output the name of the day (Monday — 1, Tuesday — 2, etc.).

  
Expected output:

Please enter a number from 1 to 7: 
2
The result: The 2-d day of the week is Tuesday

Please enter a number from 1 to 7:  
9
The result: The are no such days, please enter 1, 2, ..., 7

[Solution and Project name: Lesson_2Task8, file name L2Task8.cs]