Develop Reference

Understanding Marching Square algorithm

The following picture is retrieved from Wikipedia:
I haven't understood this part:
I have two questions here:
Where did they obtain [8,4,1,2] from and what did they want to tell us by that?
Take a look at cell [0, 0] whose value is 13. If I go clockwise along with its contouring values, I obtain the binary string 0010 which is 2. How does the 1st cell-value become 13?
.
enum What
{
lines, surface, both
}
class Program
{
public static void Print(int[,] data, int xn, int yn)
{
for (int j = 0; j < yn; j++)
{
for (int i = 0; i < xn; i++)
{
Console.Write(data[i,j] + ", ");
}
Console.WriteLine();
}
}
public static int[,] normalize(int[,] data, int xn, int yn)
{
for (int j = 0; j < yn; j++)
{
for (int i = 0; i < xn; i++)
{
if (data[i, j] > 1)
{
data[i, j] = 0;
}
else
{
data[i, j] = 1;
}
}
}
return data;
}
public static int[,] marching_square(int x, int y, int[,] data, int isovalue, What what)
{
int xn = x;
int yn = y;
data = normalize(data, xn, yn);
int[,] bitMask = new int[xn - 1, yn - 1];
for (int j = 0; j < yn - 1; j++)
{
for (int i = 0; i < xn - 1; i++)
{
StringBuilder sb = new StringBuilder();
sb.Append(data[i, j]);
sb.Append(data[i, j + 1]);
sb.Append(data[i + 1, j]);
sb.Append(data[i + 1, j + 1]);
bitMask[i, j] = Convert.ToInt32(sb.ToString(), 2);
}
}
return bitMask;
}
static void Main(string[] args)
{
int[,] data = new int[,] {
{ 1,1,1,1,1 },
{ 1,2,3,2,1 },
{ 1,3,3,3,1 },
{ 1,2,3,2,1 },
{ 1,1,1,1,1 }
};
Print(data, 5,5);
int[,] bitMask = marching_square(5,5,data, 0, What.lines);
Print(bitMask, 4, 4);
}
}
Output:
1, 1, 1, 1, 1,
1, 2, 3, 2, 1,
1, 3, 3, 3, 1,
1, 2, 3, 2, 1,
1, 1, 1, 1, 1,
14, 10, 10, 11,
12, 0, 0, 3,
12, 0, 0, 3,
13, 5, 5, 7,
I inverted the bits. But, the output looks different.

C# flattening/expanding a 3D matrix into a jagged array

I have to flatted a 3d array in order to be serialized.
Let's start with this:
int[,,] array3D = new int[,,] {
{ { 1, 2 }, { 3, 4 }, {5,6 }, {7,8 } },
{ { 9, 10}, { 11, 12},{ 13,14} , {15,16 }},
{ { 17, 18}, { 19, 20},{ 21,22}, {23,24 } }
};
which makes it like this (something like 1,2,3,4,...,24):
So now I have this s/r
public static T[] Flatten<T>(T[,,] arr)
{
int rows0 = arr.GetLength(0);
int rows1 = arr.GetLength(1);
int rows2 = arr.GetLength(2);
T[] arrFlattened = new T[rows0 * rows1* rows2];
int i, j, k;
for (k = 0; k < rows2; k++)
{
for (j = 0; j < rows1; j++)
{
for (i = 0; i < rows0; i++)
{
var test = arr[i, j, k];
int index = i + j * rows0 + k * rows1;
arrFlattened[index] = test;
}
}
}
return arrFlattened;
}
which flattens the 3d matrix into a 1d array
I am not smart enough to understand if the procedure is correct but let's go further.
I then Expand with the following s/r
public static T[,,] Expand<T>(T[] arr, int rows0, int rows1)
{
int length = arr.GetLength(0);
int rows2 = length / rows0 / rows1;
T[,,] arrExpanded = new T[rows0, rows1, rows2];
for (int k = 0; k < rows2; k++)
{
for (int j = 0; j < rows1; j++)
{
for (int i = 0; i < rows0; i++)
{
T test = arr[i + j * rows0 + k * rows1];
arrExpanded[i, j, k] = test;
}
}
}
return arrExpanded;
}
but the result is the following:
So nothing like 1,2,3,4,5....24
I know that the error might be a trivial one but try as I might I can't find it.
Thank in advance.
Patrick
Thanks for helping all 3 solution were amazing and working but I chose the one more easily to understand and debug for me

I am assuming that you want to know what is the mistake in your code more than you want to know the quickest way to get to the answer. Your index calculation is wrong. You are calculating it like this:
int index = i + j * rows0 + k * rows1;
But you actually need to multiply the last term not just by rows1 but by rows0 too:
int index = i + j * rows0 + k * rows1 * rows0;
Also, it makes sense to swap the order of dimensions that are iterated in for loops to get results in order. The final code for that would be:
public static T[] Flatten<T>(T[,,] arr)
{
int rows0 = arr.GetLength(0);
int rows1 = arr.GetLength(1);
int rows2 = arr.GetLength(2);
T[] arrFlattened = new T[rows0 * rows1* rows2];
int i, j, k;
for (k = 0; k < rows0; k++)
{
for (j = 0; j < rows1; j++)
{
for (i = 0; i < rows2; i++)
{
var test = arr[k, j, i];
int index = i + j * rows2 + k * rows1 * rows2;
arrFlattened[index] = test;
}
}
}
return arrFlattened;
}
public static T[,,] Expand<T>(T[] arr, int rows0, int rows1)
{
int length = arr.GetLength(0);
int rows2 = length / rows0 / rows1;
T[,,] arrExpanded = new T[rows0, rows1, rows2];
int i, j, k;
for (k = 0; k < rows0; k++)
{
for (j = 0; j < rows1; j++)
{
for (i = 0; i < rows2; i++)
{
T test = arr[i + j * rows2 + k * rows1 * rows2];
arrExpanded[k, j, i] = test;
}
}
}
return arrExpanded;
}

You could give this a go:
void Main()
{
int[,,] array3D = new int[,,]
{
{ { 1, 2 }, { 3, 4 }, {5,6 }, {7,8 } },
{ { 9, 10}, { 11, 12},{ 13,14} , {15,16 }},
{ { 17, 18}, { 19, 20},{ 21,22}, {23,24 } }
};
var flattened = array3D.Cast<int>().ToArray();
var restored = Expand(flattened, 3, 4);
}
public static T[,,] Expand<T>(T[] arr, int rows0, int rows1)
{
int length = arr.GetLength(0);
int rows2 = length / rows0 / rows1;
int x = 0;
T[,,] arrExpanded = new T[rows0, rows1, rows2];
for (int i = 0; i < rows0; i++)
{
for (int j = 0; j < rows1; j++)
{
for (int k = 0; k < rows2; k++)
{
T test = arr[x++];
arrExpanded[i, j, k] = test;
}
}
}
return arrExpanded;
}
It worked fine for me.

With a help of Linq OfType<T>(), it's easy to have int[] from any multidimensional array:
var result = source.OfType<int>().ToArray();
Demo:
using System.Linq;
...
int[,,] array3D = new int[,,] {
{ { 1, 2}, { 3, 4}, { 5, 6}, { 7, 8 } },
{ { 9, 10}, { 11, 12}, { 13, 14}, {15, 16 } },
{ { 17, 18}, { 19, 20}, { 21, 22}, {23, 24 } },
};
var result = array3D.OfType<int>().ToArray();
Console.Write(string.Join(", ", result));
Outcome:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
We can use modulo arithmetics to Expand array back:
private static T[,,] Expand<T>(T[] value, int length1, int length2, int length3) {
T[,,] result = new T[length1, length2, length3];
for (int i = 0; i < value.Length; ++i) {
int r = i / (length3 * length2);
int c = i / length3 % length2;
int h = i % length3;
result[r, c, h] = value[i];
}
return result;
}
E.g.
int[,,] back = Expand(result, 3, 4, 2);

To flatten a multidimensional array just use Cast<T>().ToArray().
var d3 = new int[,,]
{
{ { 1, 2 }, { 3, 4 }, {5,6 }, {7,8 } },
{ { 9, 10}, { 11, 12},{ 13,14} , {15,16 }},
{ { 17, 18}, { 19, 20},{ 21,22}, {23,24 } }
};
var d1 = d3.Cast<int>().ToArray();
Console.WriteLine(string.Join(" ", d1));
Gives:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
To expand use this:
static int[,,] Expand(int[] array, int size2, int size3)
{
var size = new[] { array.Length / size2 / size3, size2, size3 };
var res = Array.CreateInstance(typeof(int), size);
for (var i = 0; i < array.Length; i++)
res.SetValue(array[i], GetMultidimensionalIndex(i, size));
return (int[,,])res;
}
static int[] GetMultidimensionalIndex(int index, int[] size)
{
var factors = size.Select((item, i) => size.Skip(i).Aggregate((a, b) => a * b)).ToArray();
var factorsHelper = factors.Zip(factors.Skip(1).Append(1), (Current, Next) => new { Current, Next }).ToArray();
return factorsHelper.Select(item => index % item.Current / item.Next).ToArray();
}
Usage:
var d3 = new int[,,]
{
{ { 1, 2 }, { 3, 4 }, {5,6 }, {7,8 } },
{ { 9, 10}, { 11, 12},{ 13,14} , {15,16 }},
{ { 17, 18}, { 19, 20},{ 21,22}, {23,24 } }
};
Console.WriteLine("Original:");
Print3DArray(d3);
var flat = d3.Cast<int>().ToArray();
Console.WriteLine("Flat:");
Console.WriteLine(string.Join(" ", flat));
var expanded = Expand(flat, d3.GetLength(1), d3.GetLength(2));
Console.WriteLine("Expanded:");
Print3DArray(expanded);
with helper method:
static void Print3DArray(int[,,] array)
{
Console.WriteLine("{");
for (int i = 0; i < array.GetLength(0); i++)
{
Console.Write(" {");
for (int j = 0; j < array.GetLength(1); j++)
{
Console.Write(" {");
for (int k = 0; k < array.GetLength(2); k++)
{
Console.Write($" {array[i, j, k]}");
}
Console.Write(" }");
}
Console.WriteLine(" }");
}
Console.WriteLine("}");
}
Gives:
Original:
{
{ { 1 2 } { 3 4 } { 5 6 } { 7 8 } }
{ { 9 10 } { 11 12 } { 13 14 } { 15 16 } }
{ { 17 18 } { 19 20 } { 21 22 } { 23 24 } }
}
Flat:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Expanded:
{
{ { 1 2 } { 3 4 } { 5 6 } { 7 8 } }
{ { 9 10 } { 11 12 } { 13 14 } { 15 16 } }
{ { 17 18 } { 19 20 } { 21 22 } { 23 24 } }
}

Average Array for int values in a 2D String Array

I am having a bit of trouble with my program which holds student names and grades in a 2D string array. Basically, I have a second (1D) array that will hold average grade for each student.
code so far:
class Program
{
static void Main(string[] args)
{
// Create a 2D array for names, and their grades, and an array for average grades
string[,] studentGrades = new string[5, 8];
int[] average = new int[studentGrades.GetLength(0)];
// Set student names/grades manually
studentGrades[0, 0] = "Steve";
studentGrades[0, 1] = "69";
studentGrades[0, 2] = "80";
studentGrades[0, 3] = "66";
studentGrades[0, 4] = "75";
studentGrades[0, 5] = "90";
studentGrades[0, 6] = "69";
studentGrades[0, 7] = "98";
studentGrades[1, 0] = "Bob";
studentGrades[1, 1] = "73";
studentGrades[1, 2] = "67";
studentGrades[1, 3] = "65";
studentGrades[1, 4] = "91";
studentGrades[1, 5] = "48";
studentGrades[1, 6] = "33";
studentGrades[1, 7] = "94";
studentGrades[2, 0] = "Lewis";
studentGrades[2, 1] = "67";
studentGrades[2, 2] = "80";
studentGrades[2, 3] = "66";
studentGrades[2, 4] = "75";
studentGrades[2, 5] = "90";
studentGrades[2, 6] = "69";
studentGrades[2, 7] = "63";
studentGrades[3, 0] = "Sara";
studentGrades[3, 1] = "55";
studentGrades[3, 2] = "58";
studentGrades[3, 3] = "63";
studentGrades[3, 4] = "70";
studentGrades[3, 5] = "55";
studentGrades[3, 6] = "55";
studentGrades[3, 7] = "76";
studentGrades[4, 0] = "Xavier";
studentGrades[4, 1] = "22";
studentGrades[4, 2] = "27";
studentGrades[4, 3] = "25";
studentGrades[4, 4] = "19";
studentGrades[4, 5] = "42";
studentGrades[4, 6] = "18";
studentGrades[4, 7] = "32";
// Loop the array dimensions and output/format output the names/grades
for (int name = 0; name < studentGrades.GetLength(0); name++)
{
for (int grade = 0; grade < studentGrades.GetLength(1); grade++)
{
Console.WriteLine(studentGrades[name, grade]);
}
Console.WriteLine("");
}
for (int i = 0; i < studentGrades.GetLength(0); i++)
{
for (int j = 0; j < studentGrades.GetLength(1); j++)
{
average[j] += int.Parse(studentGrades[i, j]);
}
}
}
}
I get an un-handled exception in regards to the input string not being in the correct format where the average is set.
All help is appreciated!
Update
I've reviewed the solutions of code so far below, and I'm still having issues with getting the grade average to work as intended. I have 5 students with 7 grades. I want the program to output the average of each persons grades below their column.
Code:
static void Main(string[] args)
{
// Create a 2D array for names, and their grades, and an array for average grades
string[,] studentGrades = new string[5, 8];
int[] average = new int[studentGrades.GetLength(1)];
// Set student names/grades manually
//As done above, excluded for brevity reasons
// Loop the array dimensions and output/format output the names/grades
for (int grade = 0; grade < studentGrades.GetLength(1); grade++)
{
for (int name = 0; name < studentGrades.GetLength(0); name++)
{
// Composite formatting is used to align names/grades in grid -- specifically the alignment component.
// Making the value higher (more neg) will increase spacing between elements
// Positive number would right align elements instead
Console.Write("{0, -15}", studentGrades[name, grade]);
}
// Moves each printed grade to a new line
Console.WriteLine("");
}
for (int i = 0; i < studentGrades.GetLength(0); i++)
{
for (int j = 1; j < studentGrades.GetLength(1); j++)
{
average[j] += int.Parse(studentGrades[i, j]);
}
average[i] /= studentGrades.GetLength(1) - 1;
}
for (int i = 0; i <= average.GetLength(0) - 1; i++)
{
Console.Write("{0, -15}", i);
}
Console.WriteLine("");
}
Update 2
It seems that the average array is not being properly populated. It seems to just print out 1, 2, 3, 4, 5, 6, 7 if I remove the average division. Furthermore, if I change averages' length to 5 -- or the length of the amount of names since there will only be 5 values, it breaks. This is likely because it's trying to add 7 items to a 5 item array.

Every studentGrages[*, 0] element is not integer so you can't parse it to int
Skip the first elements
for (int i = 0; i < studentGrades.GetLength(0); i++)
{
for (int j = 1; j < studentGrades.GetLength(1); j++)
{
average[j] += int.Parse(studentGrades[i, j]);
}
}

You have to change this part of code:
// Store the average as a double array, otherwise you can't have averages with decimal values.
double[] average = new double[studentGrades.GetLength(0)];
for (int i = 0; i < studentGrades.GetLength(0); i++)
{
// Start from j = 1, as j = 0 would get a name instead of a grade.
for (int j = 1; j < studentGrades.GetLength(1); j++)
{
// Here use average[i] instead of average[j], because you want
// the average grade for each student.
average[i] += int.Parse(studentGrades[i, j]);
}
// Finish calculating the average.
// GetLength(0) - 1 because the first item is a name, not a grade.
average[i] /= studentGrades.GetLength(1) - 1;
}
for (int i = 0; i <= average.GetLength(0) - 1; i++)
{
// Show at most 2 decimal digits.
Console.Write("{0, -15:#.##}", average[i]);
}

Your trying to include the string of the names (on the 0 index) with the average. e.g int.Parse("Steve") which is causing the exception, just skip on the first element on each colum.
for (int j = 1; j < studentGrades.GetLength(1); j++)

As other have rightly pointed out, you need to change the 0 to a 1 in the following line:
for (int j = 1; j < studentGrades.GetLength(1); j++)
Otherwise you're going to try to parse the name as an integer.
Also you need to change the index on average inside the loop to i rather than j.
average[i] += int.Parse(studentGrades[i, j]);
The other issue that you're going to have is that you're using integer mathematics - so when you do something like 7 / 2 you get an answer of 3 and not 3.5.
If I were you, and you don't want to change your data structure, I would do it this way:
var results =
studentGrades
.Cast<string>()
.Select((x, n) => new { x, n })
.GroupBy(xn => xn.n / studentGrades.GetLength(1), xn => xn.x)
.Select(xs => new
{
student = xs.First(),
average = xs.Skip(1).Select(x => int.Parse(x)).Average(),
})
.ToArray();
That gives me:
Alternatively, I would suggest that you change your data structure to this:
var studentGrades = new []
{
new { student = "Steve", grades = new [] { 69, 80, 66, 75, 90, 69, 98, } },
new { student = "Bob", grades = new [] { 73, 67, 65, 91, 48, 33, 94, } },
new { student = "Lewis", grades = new [] { 67, 80, 66, 75, 90, 69, 63, } },
new { student = "Sara", grades = new [] { 55, 58, 63, 70, 55, 55, 76, } },
new { student = "Xavier", grades = new [] { 22, 27, 25, 19, 42, 18, 32, } },
};
Then this should work for you:
var results =
studentGrades
.Select(sg => new
{
sg.student,
average = sg.grades.Average(),
})
.ToArray();

How to print 2D array to console in C#

I dont't have any code for this, but I do want to know how I could do this. I use visual studio 2010 C# if that matters.
Thanks
Jason

public static void Print2DArray<T>(T[,] matrix)
{
for (int i = 0; i < matrix.GetLength(0); i++)
{
for (int j = 0; j < matrix.GetLength(1); j++)
{
Console.Write(matrix[i,j] + "\t");
}
Console.WriteLine();
}
}

you can print it all on one line
int[,] array2D = new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } };
Console.WriteLine(String.Join(" ", array2D.Cast<int>()));
output
1 2 3 4 5 6 7 8

You should read MSDN:Using foreach with Arrays
int[,] numbers2D = new int[3, 2] { { 9, 99 }, { 3, 33 }, { 5, 55 } };
// Or use the short form:
// int[,] numbers2D = { { 9, 99 }, { 3, 33 }, { 5, 55 } };
foreach (int i in numbers2D)
{
System.Console.Write("{0} ", i);
}
// Output: 9 99 3 33 5 55

//The following are three ways to print any 2d arrays to console:
int[,] twoDArray = new int[3, 4]{ {2,5,55,44},{10,45,5,22 },{ 67,34,56,77} };
Console.WriteLine("Array Code Out Method:1");
int rows = twoDArray.GetLength(0); // 0 is first dimension, 1 is 2nd
//dimension of 2d array
int cols = twoDArray.GetLength(1);
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
Console.Write("\t" + twoDArray[i, j]);
//output: 2 5 55 44 10 45 5 22 67 34 56 77
}
}
Console.WriteLine("Array Code Out Method: 2");
for (int x = 0; x <= twoDArray.GetUpperBound(0); x++)
{
for (int y = 0; y <= twoDArray.GetUpperBound(1); y++)
{
Console.Write("\t"+ twoDArray[x,y]);
//output: 2 5 55 44 10 45 5 22 67 34 56 77
}
}
Console.WriteLine("Array Code Out Method:3");
foreach (int items in twoDArray)
{
Console.Write(""+ "\t" +items);
//output: 2 5 55 44 10 45 5 22 67 34 56 77
}
//string example
string[,] friendNames = new string[,] { {"Rosy","Amy"},
{"Peter","Albert"}
};
foreach (string str in friendNames)
{
Console.WriteLine(str);
}

The following is an example...
static void Main()
{
// A. 2D array of strings.
string[,] a = new string[,]
{
{"ant", "aunt"},
{"Sam", "Samantha"},
{"clozapine", "quetiapine"},
{"flomax", "volmax"},
{"toradol", "tramadol"}
};
// B. Get the upper bound to loop.
for (int i = 0; i <= a.GetUpperBound(0); i++)
{
string s1 = a[i, 0]; // ant, Sam, clozapine...
string s2 = a[i, 1]; // aunt, Samantha, quetiapine...
Console.WriteLine("{0}, {1}", s1, s2);
}
Console.WriteLine();
}

int[,] matrix = new int[2, 2] { {2, 2}, {1, 1} };
for (int i = 0; i < matrix.GetLength(0); i++)
{
for (int k = 0; k < matrix.GetLength(1); k++ )
{
//put a single value
Console.Write(matrix[i,k]);
}
//next row
Console.WriteLine();
}

private int[,] MirrorH(int[,] matrix)
{
int[,] MirrorHorizintal = new int[4, 4];
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j ++)
{
MirrorHorizintal[i, j] = matrix[i, 3 - j];
}
}
return MirrorHorizintal;
}

Try like this..
int[,] matrix = new int[3, 3]
{
{1, 2, 3},
{4, 5, 6},
{7, 8, 9},
};
int rowLength = matrix.GetLength(0);
int colLength = matrix.GetLength(1);
for (int i = 0; i < rowLength; i++)
{
for (int j = 0; j < colLength; j++)
{
Console.Write(string.Format("{0} ", matrix[i, j]));
}
Console.Write(Environment.NewLine + Environment.NewLine);
}
Console.Read();

Below is multiple solution to how to implement multidimentional array, I think it is pretty straight forward in c#.
using System;
using System.Collections.Generic;
namespace DataStructure
{
class Program : SortedZeros
{
static void Main(string[] args)
{
// Two-Dimensional Array
int[,] numbers2D = new int[3, 2]
{
{ 9, 99 },
{ 3, 33 },
{ 5, 55 }
};
// 3 * 3
int[,] dataTest2D = new int[3, 3]
{
{3, 5, 7},
{4, 3, 8},
{9, 6, 9},
};
// A similar array with string elements.
int[,] matrix = new int[4, 4]
{
{1, 2, 3, 6},
{4, 5, 6, 4},
{7, 8, 9, 6},
{7, 8, 9, 2},
};
int rowLength = matrix.GetLength(0);
int colLength = matrix.GetLength(0);
for (int i = 0; i < rowLength; i++)
{
for (int j = 0; j < colLength; j++)
{
Console.Write(string.Format("{0} ", matrix[i, j]));
}
Console.Write(Environment.NewLine + Environment.NewLine);
}
// using foreach to print out the 2 * 2 in one straightline
foreach (int i in numbers2D)
{
Console.Write("{0} ", i);
}
Console.WriteLine();
Console.WriteLine();
for (int i = 0; i < dataTest2D.GetLength(0); i++)
{
for (int j = 0; j < dataTest2D.GetLength(1); j++)
{
Console.Write(string.Format("{0} ", dataTest2D[i, j]));
}
Console.Write(Environment.NewLine + Environment.NewLine);
}
}
}
}

Explanation:
1. create an array
2. Create 2 for loops (one inside the other)
3. In "j" loop, pass matrix (roomString in our case) as parameter.
4. Add a "+" symbol (concatenate) it with a " " (empty space)
5. In "i" loop, have a "cw tab tab" --> Console.WriteLine();
Code:
string[,] roomString = new string[4, 4]
{
{"0","0","0","0" },
{"0","0","0","0" },
{"0","0","0","0" },
{"0","0","0","0" }
};
for (int i = 0; i < roomString.GetLength(0); i++)
{
for (int j = 0; j < roomString.GetLength(1); j++)
{
Console.Write(roomString[i,j]+" ");
}
Console.WriteLine();
}

Helper function to get any row:
public static int[] GetRow(int[,] mat, int rowNumber)
=> Enumerable.Range(0, mat.GetLength(1))
.Select(i => mat[rowNumber, i])
.ToArray();
Print row values in new line:
int[,] mat = new int[2,2];
for (int i =0; i < mat.GetLength(0); i++)
{
Console.WriteLine(string.Join(",", GetRow(mat, i)));
}

Do it like this:
static public void Print2DArray(int[][] A)
{
foreach (int[] row in A)
{
foreach (int element in row)
{
Console.Write(element.ToString() + " ");
}
Console.WriteLine();
}
}

Sum, Subtract and Multiply arrays

I've got the following arrays:
int[,] myArray1 = new int[2, 3] { { 1, 2, 3 }, { 4, 6, 8 } };
int[,] myArray2 = new int[2, 3] { { 6, 4, 3 }, { 8, 2, 8 } };
What I'd like to know how to do is:
Create a new array with the sum of myArray1 and myArray2
Create a new array with the subtraction of myArray1 and myArray2
Create a new array with the multiplication of myArray1 and myArray2
Result of sum would be:
int[,] myArray3 = new int[2, 3] { { 7, 6, 0 }, { -4, 4, 0 } };
Result of subtraction would be:
int[,] myArray3 = new int[2, 3] { { 5, 2, 6 }, { 12, 8, 16 } };
Result of multiplication would be:
int[,] myArray3 = new int[2, 3] { { 6, 8, 9 }, { 32, 12, 64 } };
Can this be done similar to printing out the arrays, with for loops? I tried looking for examples but found none that I could use for my specific problem.

int[,] a3 = new int[2,3];
for(int i = 0; i < myArray1.GetLength(0); i++)
{
for(int j = 0; j < myArray1.GetLength(1); j++)
{
a3[i,j] = myArray1[i,j] + myArray2[i,j];
a3[i,j] = myArray1[i,j] - myArray2[i,j];
a3[i,j] = myArray1[i,j] * myArray2[i,j];
}
}
need to store a3 before doing a new calculation obviously

For Sum:
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 3; j++)
{
myArray3[i, j] = myArray1[i, j] + myArray2[i, j];
}
}
For Subtraction:
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 3; j++)
{
myArray3[i, j] = myArray2[i, j] - myArray1[i, j];
}
}
For Multiplication:
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 3; j++)
{
myArray3[i, j] = A[i, j] * B[i, j];
}
}

Yes this would be done exactly like printing out the arrays with for loops
c# has foreach loops which would be even easier to use
Note: I get the idea this is for homework so I'm not going to give a 100% conclusive end all be all answer.
int[,] myArray1 = new int[2, 3] { { 1, 2, 3 }, { 4, 6, 8 } };
int[,] myArray2 = new int[2, 3] { { 6, 4, 3 }, { 8, 2, 8 } };
foreach (int[] a1 in myArray1)
{
foreach(int i in a1)
{
//operation here
//you get the idea
}
}

If you want to do array manipulation faster use the C# Parallel.For loop from System.Threading.Tasks:
For simple arithmetic parallelizing the outer loop is much faster than not on a modern PC processor. For more complex operations, or for small array sizes, the parallel version can be slower for various reasons.
Thus, use a stopwatch to time your matrix operations, and use the fastest solution. Parallelization makes doing array / image processing in C# much faster if implemented right.
Beware of overflowing your datatypes after arithmetic operations and also sharing variables between multiple threads (see System.Threading.Interlocked for help with that)...
Subtraction below. Similar for addition and multiplication:
Parallel.For(0, array.GetLength(1), y=>
{
for (int x = 0; x < array.GetLength(0); x++)
{
difference[x,y] = minuend[x,y] - subtrahend[x,y];
}
}
});

If you want to use a for loop, you can iterate through the rows/columns of the multi-d array as follows:
for (int i = 0; i < myArray1.GetLength(0); i++)
{
for (int j = 0; j < myArray1.GetLength(1); j++)
{
// Here, you can access the array data by index, using i and j.
// Ex, myArray1[i, j] will give you the value of 1 in the first iteration.
}
}
Note: When you pass a value into the Array's GetLength method, it represents the dimension of the array. See http://msdn.microsoft.com/en-us/library/system.array.getlength.aspx