Hello looking for solution to fill 2D array with random values from 1-8 without 3 same numbers next to each other in a column or in a row.
Random random = new Random();
for (var row = 0; row < RowCount; row++)
{
for (var column = 0; column < RowCount; column++)
{
tiles[row, column] = random.Next(1, 8);
}
}
Idea is simple: fill your matrix from right to left and from top to down. To avoid duplicates at any cell look two cells up and two cells left, and if they have same value, call random.Next(..) again. Next code will create that matrix:
// this method checks cells that up to current
private static bool EqualsUp(int i, int j, int[,] matrix, int value) => i >= 0 && matrix[i, j] == value;
// this method checks cells that left to current
private static bool EqualsLeft(int i, int j, int[,] matrix, int value) => j >= 0 && matrix[i, j] == value;
public static int[,] GenerateMatrix(int h, int w)
{
var matrix = new int[h, w];
var random = new Random();
for (var i = 0; i < h; ++i)
for (var j = 0; j < w; ++j)
while (true)
{
var cellValue = random.Next(1, 9); // note: second value is exclusive, so to generate values from 1 to 8 pass 9 as second argument
if (EqualsUp(i - 1, j, matrix, cellValue) && EqualsUp(i - 2, j, matrix, cellValue))
continue; // need to regenerate cellValue
if (EqualsLeft(i, j - 1, matrix, cellValue) && EqualsLeft(i, j - 2, matrix, cellValue))
continue; // need to regenerate cellValue
matrix[i, j] = cellValue;
break;
}
return matrix;
}
Related
I have a string array and have to fill up a DataGridView with it by picking a random next cell. I want to use all items of the array but avoid to pick a cell I already filled up. It is fine if there are empty cells but I have to use all items.
What I tried:
foreach (var item in myarray)
{
y = random.Next(0, 5);
x = random.Next(0, t.Rows.Count);
t.CurrentCell = t[y, x];
for (int j = 0; j < t.Columns.Count; j++)
{
for (int k = 0; k < t.Rows.Count; k++)
{
if (t.Rows[k].Cells[j].Value == null)
{
t.CurrentCell.Value = item;
}
}
}
}
Many thanks!
You can assign a number to each cell from left to right, like for 4x4 matrix each cell will be numbered from 0 to 15. After that you can shuffle 0...15 array of integers and iterate over that array by assigning a string to the corresponding cell which you can get by converting a number from array (cellNumber) back to coordinates like this:
(cellNumber / rowsCount, cellNumber % columnsCount).
Consider following source code:
private static Random rng = new Random();
public static void Shuffle<T>(this IList<T> list)
{
int n = list.Count;
while (n > 1) {
n--;
int k = rng.Next(n + 1);
T value = list[k];
list[k] = list[n];
list[n] = value;
}
}
public static (int x, int y) GetCoordinates(int cellNumber, int rowsCount, int columnsCount) {
return (cellNumber / rowsCount, cellNumber % columnsCount);
}
public static void Main()
{
var rowsCount = 4;
var columnsCount = 4;
var cellNumbers = Enumerable.Range(0,rowsCount*columnsCount - 1).ToList();
cellNumbers.Shuffle();
foreach (var cellCoordinates in cellNumbers.Select(x => GetCoordinates(x, rowsCount, columnsCount))) {
Console.WriteLine($"{cellCoordinates.x},{cellCoordinates.y}");
}
}
[8, 8] I have a 2-dimensional array creating rows and columns [i, j].
I want to check if there is an object in a single row. For example, line 4 or line 1.
You can run a for lopp and check.
int i = 0; //or 3 //here you can set the row number
bool exists = false;
int value = 4;
for(int j = 0; j < array.GetLength(1); j++)
{
if(array[i, j] == value)
{
exists = true;
break;
}
}
The extension :
public static T[,] SubArray<T>(this T[,] values, int row_min, int row_max, int col_min, int col_max)
{
int num_rows = row_max - row_min + 1;
int num_cols = col_max - col_min + 1;
T[,] result = new T[num_rows, num_cols];
int total_cols = values.GetUpperBound(1) + 1;
int from_index = row_min * total_cols + col_min;
int to_index = 0;
for (int row = 0; row <= num_rows - 1; row++)
{
Array.Copy(values, from_index, result, to_index, num_cols);
from_index += total_cols;
to_index += num_cols;
}
return result;
}
work well for 2D arrays arrays whose GetLowerBound(0) and GetLowerBound(1) are equal to zero. For instance if
int[,] arr1 = new int[5, 4];
for (int i = 0; i < 5; ++i)
{
for (int j = 0; j < 4; ++j)
{
arr1[i, j] = i + j;
}
}
var arr1sub = arr1.SubArray(2, 3, 1, 3);
Then arr1sub is the 2d array with 2 rows and 3 colums (boths with indexes starting at 0)
3 4 5
5 6 7
Now if I look at the case where the initial array as indexes not starting at zero :
int[,] arr2 = (int[,])Array.CreateInstance(typeof(int), new int[] { 5, 4 }, new int[] { 3, 1 });
for (int i = arr2.GetLowerBound(0); i <= arr2.GetUpperBound(0); ++i)
{
for (int j = arr2.GetLowerBound(1); j <= arr2.GetUpperBound(1); ++j)
{
arr2[i, j] = i - arr2.GetLowerBound(0) + j - arr2.GetLowerBound(1);
}
}
var arr2sub = arr2.SubArray(5, 6, 2, 4);
the last line of previous code snippet will trigger an exception in the SubArray extension function at the line
Array.Copy(values, from_index, result, to_index, num_cols);
for row equal to zero.
I understand of the 2d array arr1 (with zero based indexes) is layed out in memory but not how the 2d array arr2 (with non-zero-based indexes) is layed out in memory, hence my use of Array.Copy must be wrong in this case, but I don't see why.
You are not calculating total_cols and from_index correctly.
public static T[,] SubArray<T>(this T[,] values, int row_min, int row_max, int col_min, int col_max)
{
int num_rows = row_max - row_min + 1;
int num_cols = col_max - col_min + 1;
T[,] result = new T[num_rows, num_cols];
int total_cols = values.GetLength(1);
int from_index = (row_min - values.GetLowerBound(0)) * total_cols + (col_min - values.GetLowerBound(1)) + values.GetLowerBound(0);
int to_index = 0;
for (int row = 0; row <= num_rows - 1; row++)
{
Array.Copy(values, from_index, result, to_index, num_cols);
from_index += total_cols;
to_index += num_cols;
}
return result;
}
total_cols is the obvious one; as for from_index, I cannot find any documentation on that, but it would appear that sourceIndex in Array.Copy starts counting from sourceArray.GetLowerBound(0) and not from zero, which is not necessarily immediately obvious given that this index keeps growing across rows and columns.
I don't know how to shuffle 2D array without duplicate elements. Can anyone help me to shuffle a 2D array?
Here is what I have so far:
public class Shuffle2DArray
{
public Shuffle2DArray ()
{
}
public static void Main(string[] args)
{
int[,] a = new int[3, 3] { { 1, 2, 3, }, { 6, 7, 8 }, { 11, 12, 13 } };
Shuffle2DArray shuffle = new Shuffle2DArray ();
shuffle.getshuffle2D (a);
}
void getshuffle2D(int[,] arr)
{
Random ran = new Random ();
for (int i = 0; i < arr.GetLength (0); i++) {
for (int j = 0; j < arr.GetLength (1); j++) {
int m = ran.Next(arr.GetLength (0)-1);
int n = ran.Next(arr.GetLength (1)-1);
int temp = arr[0,j];
arr[i,0] = arr[m,n+1];
arr[m,n] = temp;
Console.Write(arr[i,j]+ "\t");
}
Console.WriteLine();
}
}
}
Well, I would say shuffle the 2d array the same way as you shuffle the 1d array.
For instance, Fisher–Yates shuffle for 1d array is something like this
public static class Utils
{
public static void Swap<T>(ref T a, ref T b) { var temp = a; a = b; b = temp; }
public static void RandomShuffle<T>(this T[] target, Random random = null)
{
if (target.Length < 2) return;
if (random == null) random = new Random();
for (int i = target.Length - 1; i > 0; i--)
{
int j = random.Next(i + 1);
if (i != j) Swap(ref target[i], ref target[j]);
}
}
}
All you need is to realize that having a 2d array
T[,] array
and accessing the element of the array
array[row, column]
that
row = index / columnCount
column = index % columnCount
where
index = [0, array.Lenght - 1] corresponds to the index in 1d array
columnCount = array.GetLength(1)
adding the 2d version function to the class above is trivial
public static class Utils
{
// ...
public static void RandomShuffle<T>(this T[,] target, Random random = null)
{
if (target.Length < 2) return;
if (random == null) random = new Random();
int columnCount = target.GetLength(1);
for (int i = target.Length - 1; i > 0; i--)
{
int j = random.Next(i + 1);
if (i != j) Swap(ref target[i / columnCount, i % columnCount], ref target[j / columnCount, j % columnCount]);
}
}
}
Sample usage:
int[,] a = new int[3, 3] { { 1, 2, 3, }, { 6, 7, 8 }, { 11, 12, 13 } };
a.RandomShuffle();
You need to first order your array by random sequence of numbers. What you are doing now is just changing two random items of 2d array at each iterate thus it may result in duplicate items.
Look at this Sort algorithm for 1d array.
for (int i = 0; i < arr.Length - 1; i++)
{
for (int j = i + 1; j < arr.Length; j++)
{
if (arr[i] > arr[j]) // ran.Next(-1,1) == 0 // or any random condition
{
int temp = arr[i];
arr[j] = arr[i];
arr[i] = temp;
}
}
}
As you can see we need 2 loops to sort 1d array. So in order to sort 2d array we need 4 loops.
for (int i = 0; i < arr.GetLength(0); i++)
{
for (int j = 0; j < arr.GetLength(0); j++)
{
for (int k = 0; k < arr.GetLength(1); k++)
{
for (int l = 0; l < arr.GetLength(1); l++)
{
if (arr[i, k] > arr[j, l]) // ran.Next(-1,1) == 0
{
int temp = arr[i, k];
arr[i, k] = arr[j, l];
arr[j, l] = temp;
}
}
}
}
}
Then write another algorithm to print items.
for (int i = 0; i < arr.GetLength(0); i++)
{
for (int j = 0; j < arr.GetLength(1); j++)
{
Console.Write(arr[i, j] + "\t");
}
Console.WriteLine();
}
This was Sort algorithm. Now if you just change this condition with random one you sort your array by random.
Change if (arr[i, k] > arr[j, l])
To if (ran.Next(-1,1) == 0). this is just randomly true or false.
I've adapted QuickSort Method to sort Array's Row.
Here's the code:
That one works fine
static void QuickSort(int lowBound, int highBound, int[] a)
{
int temp = 0;
int x = random.Next(lowBound, highBound);
int pivot = a[x];
int i = lowBound;
int j = highBound;
do
{
while (a[i] < pivot) i++;
while (pivot < a[j]) j--;
if (i <= j)
{
temp = a[i]; //changes an element smaller than the pivot...
a[i] = a[j];//... with the greater one
a[j] = temp;
i++; j--;
}
}
while (i <= j);
if (lowBound < j) { QuickSort(lowBound, j, a); }//recursion
if (i < highBound){ QuickSort(i,highBound, a); }
}
Here's the problematic method
static void QuickSortMatrix(int[,] a)
{
int n = a.GetLength(0);
int m = a.GetLength(1);
for (int i = 0; i < n; i++)
{
QuickSortRow(0, m - 1, i, a);
}
for (int j = 0; j < m; j++)
{
QuickSortRow(0, n - 1, j, a);
}
}
static void QuickSortRow(int lowBound, int highBound, int row, int[,] a)
{
int temp = 0;
int x = random.Next(lowBound, highBound);
int pivot = a[row,x];
int p = lowBound;
int q = highBound;
do
{
while (a[row,p] < pivot) p++;
while (pivot < a[row,q]) q--;
if (p <= q)
{
temp = a[row,p];
a[row,p] = a[row,q];
a[row,q] = temp;
p++; q--;
}
}
while (p <= q);
if (lowBound < q) { QuickSortRow(lowBound, q, row, a); }
if (p < highBound) { QuickSortRow(p, highBound,row, a); }
}
At first when the "for" loop is executed everything's ok bur for some reason when executed recursively the row that should be constant when calling the method goes outside the matrix boundaries.
Here's my array and rows reaches value of 4
int[,] matrix =
{
{7,8,9,10,11,5},
{3,6,4,16,22,4},
{7,9,17,8,3,21},
{24,7,11,19,3,4}
};
I hope my explanation was clear enough.
Could anybody advise me? What I'm missing here?
Thank you for your kind help!
BR
Stephan
n is the number of rows in the matrix (4)
m is the number of columns in the matrix (6)
In your second loop you are going 0..m and passing that value to the row parameter. It blows up because there are more columns in the matrix than rows. i.e. It tries to read matrix[4, 0].
Note: as far as I can tell you don't need the second loop because your rows are already sorted after the first loop. Remove that and it won't throw an exception.