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Remove row from multidimensional array in jagged array

I have a jagged array with a multidimensional array and want to remove an array inside the multidimensional array. My code is:
int[][,] arr = new int[4][,];
arr[0] = new int[,] {
{ 1, 2, 3 }, // <- I want to remove this row
{ 4, 5, 6 },
{ 5, 6, 7 },
{ 8, 9, 10 } };
arr[1] = new int[,] {
{ 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 11, 12 },
{ 13, 14, 15, 16 } };
arr[2] = new int[,] {
{ 1, 2, 3, 4, 5 },
{ 5, 6, 7, 8, 9 },
{ 10, 11, 12, 13, 14 },
{ 15, 16, 17, 18, 19 } };
arr[3] = new int[,] {
{ 1, 2, 3, 4, 5, 6},
{ 5, 6, 7, 8, 9, 10},
{ 11, 12, 13, 14, 15, 16 },
{ 17, 18, 19, 20, 21, 22 } };
int[,] removeArray = { { 1, 2, 3 } };
I tried to remove {1, 2, 3} from arr[0] by using Linq:
arr = arr
.Where((val, i) => i != 0)
.ToArray();
but this removes the whole arr[0] row. Does anyone know how I can get to remove {1,2,3} using Linq?

Unlike jagged arrays, multidimensional ones doesn't consist of arrays:
int[][] jagged = new int[][] {
new[] { 1, 2, 3 }, // <- this is an array
new[] { 4, 5 }, // <- this is another array
};
int[,] array2D = new int[,] {
{ 1, 2, 3 }, // <- not an array
{ 4, 5, 6 }, // <- not an array
};
So if you want to "remove" row from 2d array, you have to recreate it; something like this:
private static T[,] RemoveRows<T>(T[,] source, T[] row) {
if (row.Length != source.GetLength(1))
return source;
var keepRows = new List<int>();
for (int r = 0; r < source.GetLength(0); ++r)
for (int c = 0; c < row.Length; ++c)
if (!object.Equals(source[r, c], row[c])) {
keepRows.Add(r);
break;
}
if (keepRows.Count == source.Length)
return source;
T[,] result = new T[keepRows.Count, source.GetLength(1)];
for (int r = 0; r < keepRows.Count; ++r)
for (int c = 0; c < result.GetLength(1); ++c)
result[r, c] = source[keepRows[r], c];
return result;
}
and then
// we remove row; let it be 1d array, not 2d one
int[] removeArray = { 1, 2, 3 };
arr = arr
.Select(array => RemoveRows(array, removeArray))
.ToArray();
please, fiddle yourself

Generate random numbers with specific interval

I'm trying to generate 3 numbers between 1 and 10. The difference between any two numbers must be smaller/equal to 2. For example: 2, 6, 9 are OK, but 2, 4, 7 are not (because 4 - 2 = 2).
private int GetGoodNumber()
{
int lastIndex = 0;
int x = 3;
int randomNumber = 0;
for (int i = 0; i < 3; i++)
{
int interval = UnityEngine.Random.Range(2, 7);
do
{
randomNumber = interval + (UnityEngine.Random.Range(0, 10));
} while (randomNumber > 10 || x <= 2);
x = (lastIndex > randomNumber) ? lastIndex - randomNumber : randomNumber - lastIndex;
lastIndex = randomNumber;
Debug.Log(randomNumber);
}
return randomNumber;
}
Unfortunately, my method does not work, does anyone know the problem.

There aren't too many combinations given this rule.
The firstNumber must be 1, 2, 3 or 4.
Based on this generate the next between firstNumber + 3 and 7.
And the last one by the same logic.
Code:
var random = new Random();
var first = random.Next(1, 4 + 1);
var second = random.Next(first + 3, 7 + 1);
var third = random.Next(second + 3, 10 + 1);

I think I would hardcode it to get correct distribution.
var x = new [,]
{
{1, 4, 7},
{1, 4, 8},
{1, 4, 9},
{1, 4, 10},
{1, 5, 8},
{1, 5, 9},
{1, 5, 10},
{1, 6, 9},
{1, 6, 10},
{1, 7, 10},
{2, 5, 8},
{2, 5, 9},
{2, 5, 10},
{2, 6, 9},
{2, 6, 10},
{2, 7, 10},
{3, 6, 9},
{3, 6, 10},
{3, 7, 10},
{4, 7, 10}
};

Mabe something like this:
public static List<int> GetRandomNumbers()
{
List<int> result = new List<int>();
for (int i = 0; i < 3; i++)
{
bool numberFit = false;
int number = 0;
do
{
number = random.Next(0, 10);
numberFit = !result.Any(x => x > number - 3 && x < number + 3);
} while (!numberFit);
result.Add(number);
}
return result;
}

Return only one subset of a given number list that sums to a target value

I was hoping someone could assist with an issue I'm having with a subset sum problem. I took the below code from another thread. What I'd like to do, ideally, is have a function that returns the first array that meets this condition: " if (s == target && partial.ToArray().Length == 7)".
Is that possible with the code I'm using below? In other words, I don't want ALL of the combinations, just the first one that meets that condition. I've tried a few things, but I'm not experienced enough at C# to really understand how to break out of the recursion or return the array to a calling function. Any help would be greatly appreciated.
private void button1_Click(object sender, EventArgs e)
{
List<int> numbers = new List<int>() { 2, 6, 6, 5, 8, 1, 3, 3, 9, 3, 6, 1, 3, 9, 1, 7, 8, 6, 8, 1, 1, 4, 4, 2, 8, 4, 5, 4, 6, 10, 1, 4, 3, 1, 2, 8, 4, 5, 9, 2, 2, 4 };
int target = 27;
sum_up(numbers, target);
}
private static void sum_up(List<int> numbers, int target)
{
sum_up_recursive(numbers, target, new List<int>());
}
private static void sum_up_recursive(List<int> numbers, int target, List<int> partial)
{
int s = 0;
foreach (int x in partial) s += x;
if (s == target && partial.ToArray().Length == 7)
Console.WriteLine("sum(" + string.Join(",", partial.ToArray()) + ")=" + target);
if (s >= target)
return;
for (int i = 0; i < numbers.Count; i++)
{
List<int> remaining = new List<int>();
int n = numbers[i];
for (int j = i + 1; j < numbers.Count; j++) remaining.Add(numbers[j]);
List<int> partial_rec = new List<int>(partial);
partial_rec.Add(n);
sum_up_recursive(remaining, target, partial_rec);
}
}
}

I'm sure there are easier ways of doing this, but to use your code, I believe this is one way you could do it:
using System.Linq;
using System.Collections.Generic;
private void button1_Click(object sender, EventArgs e)
{
List<int> numbers = new List<int>
{
2, 6, 6, 5, 8, 1, 3, 3, 9, 3, 6, 1, 3, 9, 1, 7, 8, 6, 8, 1, 1,
4, 4, 2, 8, 4, 5, 4, 6, 10, 1, 4, 3, 1, 2, 8, 4, 5, 9, 2, 2, 4
};
int target = 27;
sum_up(numbers, target);
}
private static void sum_up(List<int> numbers, int target)
{
sum_up_recursive(numbers, target, new List<int>(), 0);
}
private static void sum_up_recursive
(List<int> numbers, int target, List<int> #partial, int index)
{
int s = #partial.Sum();
if (s >= target && #partial.Count == 7)
{
Console.WriteLine("sum(" + string.Join(",", partial.ToArray()) + ")=" + target);
}
else if (s < target)
{
if( index + 7 > numbers.Count )
{
return;
}
else
{
List<int> partial_rec = numbers.GetRange(index, index + 7);
sum_up_recursive(numbers, target, partial_rec, ++index);
}
}
}

C# correct way to Iterate over 2d array as a subset 2d array

For an example if I want to iterate test and perfrorm operations on elements from that array but they have to be formatted in a particular way.
Essentially I am trying to loop over a 2d array using a 2d array.
double[,] test = {
{9, 8, 7, 6, 5, 4, 3, 2},
{8, 7, 6, 5, 4, 3, 2, 1},
{7, 6, 5, 4, 3, 2, 1, 0},
{6, 5, 4, 3, 2, 1, 0, 0},
{5, 4, 3, 2, 1, 0, 0, 0},
{4, 3, 2, 1, 0, 0, 0, 0},
{3, 2, 1, 0, 0, 0, 0, 0},
{2, 1, 0, 0, 0, 0, 0, 0},
};
double[,] subset = new double[2,2]; //used in math
What I would like to be able to do is to iterate over any size matrix (assuming that they are even sized and square) with each iteration looking like this:
Iteration 1:
subset[0,0] = test[0,0];
subset[0,1] = test[0,1];
subset[1,0] = test[1,0];
subset[1,1] = test[1,1];
So basically it selected a square same size as subset out of the large matrix.
Iteration 2:
subset[0,2] = test[0,2];
subset[1,2] = test[1,2];
subset[0,3] = test[0,3];
subset[1,3] = test[1,3];

You can do this via an extension method. A few things worth mentioning:
Using Array.Copy as opposed to manually assigning the elements should yield better performance.
Like Tom A mentioned in a comment, you should use yield return to create an IEnumerable. You can then iterate over it using a foreach loop, or perform other operations.
Implementation:
static class MatrixExtensions
{
public static IEnumerable<T[,]> ChunkMatrix<T>(this T[,] inputMatrix, int chunkWidth, int chunkHeight)
{
int inputWidth = inputMatrix.GetLength(0);
int inputHeight = inputMatrix.GetLength(1);
for(int i = 0; i < inputWidth; i += chunkWidth)
{
for(int j = 0; j < inputHeight; j += chunkHeight)
{
T[,] chunk = new T[chunkWidth, chunkHeight];
for(int k = 0; k < chunkWidth; k++)
{
int sourceIndex = i*inputWidth + k* inputWidth + j;
var destinationIndex = k* chunkHeight;
Array.Copy(inputMatrix, sourceIndex, chunk, destinationIndex, chunkHeight);
}
yield return chunk;
}
}
}
}
Usage:
double[,] test = {
{1, 2, 3, 4, 5, 6, 7, 8},
{9, 10, 11, 12, 13, 14, 15, 16},
{17, 18, 19, 20, 21, 22, 23, 24},
{25, 26, 27, 28, 29, 30, 31, 32},
{33, 34, 35, 36, 37, 38, 39, 40},
{41, 42, 43, 44, 45, 46, 47, 48},
{49, 50, 51, 52, 53, 54, 55, 56},
{57, 58, 59, 60, 61, 62, 63, 64},
};
foreach(double[,] chunk in test.ChunkMatrix(2, 2))
{
// First iteration:
// 1 2
// 9 10
//
// Second iteration:
// 3 4
// 11 12
//
// ...
}
I changed your test data to not include duplicate values, as to better illustrate the effect.
It should be noted that my implementation will not work correctly on matrices with dimensions that are not multiples of the chunks' dimensions, as it was mentioned in a comment that this will never be the case. If needed, modifying it to account for this scenario shouldn't be too hard.

Try this
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
const int COLUMNS = 8;
const int ROWS = 8;
const int SIZE = 2;
static void Main(string[] args)
{
double[,] test = {
{9, 8, 7, 6, 5, 4, 3, 2},
{8, 7, 6, 5, 4, 3, 2, 1},
{7, 6, 5, 4, 3, 2, 1, 0},
{6, 5, 4, 3, 2, 1, 0, 0},
{5, 4, 3, 2, 1, 0, 0, 0},
{4, 3, 2, 1, 0, 0, 0, 0},
{3, 2, 1, 0, 0, 0, 0, 0},
{2, 1, 0, 0, 0, 0, 0, 0},
};
for (int i = 0; i < COLUMNS; i += SIZE)
{
for (int j = 0; j < ROWS; j += SIZE)
{
for (int k = j; k < j + SIZE; k++)
{
for (int l = i; l < i + SIZE; l++)
{
Console.WriteLine("test[{0}, {1}] = {2}", k, l, test[k, l]);
}
}
}
}
Console.ReadLine();
}
}
}

I am not saying this is the best solution but while I look at the yield statement I managed to get it working using this method.
public static double[,] GetMapSection(Rectangle area, double[,] map) {
double[,] result = new double[area.Width, area.Height];
for (Int32 y = 0; y < area.Height; ++y) {
for (Int32 x = 0; x < area.Width; ++x) {
result[x, y] = map[x + area.X, y + area.Y];
}
}
return result;
}
I call it via:
List<double[,]> testChannel = new List<double[,]>();
for (int i = 0; i < Math.Sqrt(large_mapdata.Length); i+=8) {
for (int j = 0; j < Math.Sqrt(large_mapdata.Length); j+=8) {
testChannel.Add(GetMapSection(new Rectangle(i, j, 8, 8), large_mapdata));
}
}
In this example I am creating 8x8 chunks out of an array that is 32x32 in size.
I can confirm that this worked for me and is cleaner than what I had before.

how to create a 5 by 5 matrix in c# windows form

for (int i = 0; i!=5; i++)
{
for (int j=0; j!=5; j++)
{
array times[i, j] = int.Parse(Tb_First.Text);
list_Matrix.Items.Add(array times[i,j]);
}
}
or
int[,] numbers = new int[,] {{ 1 , 2 , 3, 4, 5 }, { 2, 3, 4, 5, 6 }} ;
private void button1_Click(object sender, EventArgs e)
{
for (int i = 0; i !=5; i++)
{
for (int j = 0; j !=5; j++)
{
list_Matrix.Items.Add(numbers[i,j].To String());
}
}
}
i have tried this but it isn't working.. is there any other methods to generate a 5 by 5 matrix in C# in windows form. the input is written on text box and the matrix should be in a list box. some one please help me

try it
var numbers = new int[5,5] { { 1, 2, 3, 4, 5 },
{ 2, 3, 4, 5, 6 }, { 1, 2, 3, 4, 5 }, { 2, 3, 4, 5, 6 }, { 1, 2, 3, 4, 5 }};
private void button1_Click(object sender, EventArgs e)
{
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5; j++)
{
list_Matrix.Items.Add(numbers[i,j].To String());
}
}
}

There is a source by microsoft for it
Programming guide (Multidimensional - Arrays /Matrix)
var numbers = new int[5,5] { { 1, 2, 3, 4, 5 }, { 2, 3, 4, 5, 6 }, {
1, 2, 3, 4, 5 }, { 2, 3, 4, 5, 6 }, { 1, 2, 3, 4, 5 }};
I guess discribe the int[,] is better than "var" to show that secound sample is almost correct. The problem is just the incorrect size.