Lesson # 10. A two-dimensional array

That is, in a two-dimensional array it would look like this:

  
Note: Initialization of the array:

 int [,] t = {
                {-8,-14,-19,-18},
                { 25,28, 26, 20},
                { 11,18, 20, 25}
                };

To do:

1. Print out a value of the temperature at the 2nd weather station during the 4th day and at the 3rd weather station during the 1st day (your result must be 20 and 11).
2. Print out the values of the temperature of all weather stations during the 2nd day (for loop is needed).
3. Print out the values of the temperature of all weather stations during all days.
4. Calculate the average temperature at the 3rd weather station (for loop is needed).
5. Print out the days and the weather stations’ numbers where the temperature was in the range of 24—26 degrees Celsius.

  
Expected output:

1-st task: 20  and  11
2-nd task: 25 28 26 20
3-d task:
-8  -14  -19  -18
25   28   26   20
11   18   20   25

4-th task: 18
5-th task:
station number 1  day 0
station number 1  day 2
station number 2  day 3
     
[Solution and Project name: Lesson_10Task1, file name L10Task1.cs]

To do: Ask user to input the values of the elements of a two-dimensional array 2-by-3 ([2,3]). Calculate an addition (a sum) of the elements.
   
Note 1: to declare an array with two rows and three columns use the code: 

int[,] arr=new int[2, 3];

 
Note 2: to input the values of the elements and iterate over the array the nested loop is needed:

for (int i = 0; i < 2; i++)
            {
                for (int j = 0; j < 3; j++)
                {
                   ...
                }
            }

  
Expected output:

Please enter 6 values for the matrix 2 by 3
2
5
1
6
7
8
The array:
2  5  1
6  7  8
the sum =  29

[Solution and Project name: Lesson_10Task2, file name L10Task2.cs]

To do: Ask user to input the values of the elements of a two-dimensional array 4-by-3 ([4,3]). Count positive elements within the array.
   
 
Expected output:

Please enter 12 values for the matrix 4-by-3
2  5  -1  6  7  8  1  8  6  -3  1  -6
The array:
2   5  -1
6   7   8
1   8   6
-3  1  -6
number of positive = 9

[Solution and Project name: Lesson_10Task3, file name L10Task3.cs]

To do: Create a method called FillMatrix to fill an array with random numbers in the range from -15 to 15. Create one more function to find a minimum and maximum elements of the array (FindMinMaxArr).
   
Note 1: The signature of the FindMinMaxArr function must be: 

private static void FindMinMaxArr(int[,] matrix, ref int min, ref int max)

  
Note 2: To find a minimum and a maximum you can see as you did it in the Lesson # 5 -> lab 4.

  
Expected output:

please enter the number of rows
4
please enter the number of columns
5
The array:
10   2   9  3  4
-3 -10 -14 -4  2
 2  -9  11  3 -10
-1 -13  -5 -2  3
min = -14, max = 11

[Solution and Project name: Lesson_10Task4, file name L10Task4.cs]

To do: Create a method called PlaceZero which replaces some elements of a matrix (5-by-5) with 0. Take a look at the result example below to get to know which elements should be replaced.
   
Note 1: Create methods to fill and print out a matrix.
Note 2: The signature of the PlaceZero function must be: 

static void PlaceZero(int[,] matrix)

  
Note 3: To replace elements with 0 you have to use loops.
  
Expected output:

The matrix:
10 2  9  3  6 
3  10 14 4  8
2  9  11 3  2
1  13 5  2  7
12 3  11 4  5

The resulting array:
0  0  0  0  0 
0  10 14 4  0
0  9  11 3  0
0  13 5  2  0
0  0  0  0  0

[Solution and Project name: Lesson_10Task5, file name L10Task5.cs]

To do: Create a user defined method (extension method) called FindProductOfColumn to find a product of the M-th column elements of a matrix (3-by-4) (M is entered). M is out parameter of the method. Note that you will need to create a class in the same file to have the method in it.

Note: FindProductOfColumn signature must be as follows (see pdf file of lecture #8):

public static void FindProductOfColumn(this int[,] matrix, int M,out int product)

Expected output:

The matrix:
-10 -3 -7 -4
-6   4  1  0
-5  -1 -8 -5
please enter the number of the columns (the first column is 0):
2
The product of 2-th column elements is  -64

[Solution and Project name: Lesson_10Task6, file name L10Task6.cs]

To do: Create square matrix M-by-M (M is inputted). Calculate a product of its elements within a main diagonal.

Note: a main diagonal elements are such as i=j.

Expected output:

Please enter the number for a matrix dimension:
3 
The matrix 3-by-3:
10 -7 -3 
6   1  4 
5  -8 -1 
the product of the main diagonal is -10

[Solution and Project name: Lesson_10Task7, file name L10Task7.cs]

To do: Positive integers M and N are inputted. Create a method FillMatrix to fill the elements of an integer matrix M-by-N; all the elements of the J-th column have the value X*J (J - number of a column, J = 1, ..., N), where X is a parameter of the method.
  
Note: the signature of the method must be as following:

static int[,] FillMatrix(int M, int N, int X)

Expected output:

please enter the number of rows:
3
please enter the number of columns
4
Please enter the number to multiply by:
3 
The matrix 3-by-3:
3 6 9 12
3 6 9 12
3 6 9 12 

 
[Solution and Project name: Lesson_10ExTask1, file name L10ExTask1.cs]

To do: Two matrices of the same size are given (create a method to fill the matrices with random integers). Calculate their sum by creating a new matrix for this purpose.
  
Note: the signature of the method must be as following:

static int[,] SumMat(int[,] a, int[,] b)

Expected output:

Matrix 1:
-3 8 3
-9 -6 4
6 4 -2
Matrix 2:
4 -4 1
-5 1 -1
4 8 -10
Result matrix:
1 4 4
-14 -5 3
10 12 -12

 
[Solution and Project name: Lesson_10ExTask2, file name L10ExTask2.cs]