I would like to create a multidimensional array in c#, but I`m not sure how. The array should look like this:
array1, array2, array3
array4, array5, array6
array7, array8, array9
The each small array will store 3 ints. I managed to create a multidimensional array that stores 1 array on each line, but I need to store 3 arrays on each line.
The code is below:
int[][] jaggedArray = new int[3][];
jaggedArray[0] = new int[] { 1, 3, 5 };
jaggedArray[1] = new int[] { 0, 2, 4 };
jaggedArray[2] = new int[] { 11, 22, 33 };
Your description corresponds to 2d array of arrays int[,][]:
int[] array1 = new int[] {1, 2, 3};
...
int[] array9 = new int[] {89, 562, 356};
...
// 2d array of arrays (array1..array9)
int[,][] array = new int[,][] {
{ array1, array2, array3, },
{ array4, array5, array6, },
{ array7, array8, array9, },
};
You can declare as given below. you can use jagged arrays.
int[][,] jaggedArray4 = new int[3][,]
{
new int[,] { {1,3,3}, {5,7,7},{1,2,3} },
new int[,] { {1,3,3}, {5,7,7},{1,2,3} },
new int[,] { {1,3,3}, {5,7,7},{1,2,3} }
};
Console.WriteLine(jaggedArray4[0][1,0]);//displayed first row , 2nd element array's first element
If you always have 3x3x3, you can use a 3d array:
int[,,] my3dArray = new int[3,3,3];
And you can access it like so:
my3dArray[0,0,0] = 5;
my3dArray[0,0,1] = 2;
my3dArray[1,2,0] = 41;
Console.WriteLine(myArray[1,2,0]); // prints 41
If each dimension is a variable size, you could used an array of arrays of arrays (kind of a 3d jagged array):
int[][][] myJagged = new int[3][][];
myJagged[0] = new int[3][];
myJagged[0][0] = new int[] {1, 2, 3}; // etc. until you've initialized all the arrays at all levels
Console.WriteLine(myJagged[0][0][2]); // prints 3
Alternatively, if only your last dimension is a variable size (or if it's easier to work with), you could use a 2d array of arrays:
int[,][] myArray = new int[3,3][];
myArray[0,0] = new int[] { 5, 2, 41 };
Console.WriteLine(myArray[0,0][2]); // prints 41
Related
I am wondering how to get the row of the two dimensional array like
int[3,3] a = ****
I tried a[0], but it failed. anyway to get the rwo array?
Two-dimensional array is not array of arrays. If you want to get 'row', then you need to get all items from array which have same value of some dimension. E.g. if you are getting all values from first dimension:
int[,] array = new int[4, 3] {
{ 1, 2, 3 },
{ 4, 5, 6 },
{ 7, 8, 9 },
{ 10, 11, 12 }
};
for(int i = 0; i <= array.GetUpperBound(1); i++)
Console.WriteLine(array[0,i]); // getting all items from first dimension
You can put all these items to array:
int rowIndex = 0;
int[] row = Enumerable.Range(0, array.GetUpperBound(1) + 1)
.Select(i => array[1, i])
.ToArray();
Another option will be using jagged-array instead of two-dimensional array:
int[][] array = new []{
new[] { 1, 2, 3 },
new[] { 4, 5, 6 },
new[] { 7, 8, 9 },
new[] { 10, 11, 12, 13, 14, 15 }
};
It's an array of arrays. But note that inner arrays can have different size. Getting some 'row' will look like
int[] row = array[0];
I have a List of int arrays. The list can be from 1 to 4 arrays.
I want to know how do i go about summing each array with individual threads and
placing the summed values into a new int array.
If the order of the new array is not important here you have a example
List<int[]> arraysList = new List<int[]>();
arraysList.Add(new int[] { 2, 3, 5 });
arraysList.Add(new int[] { 2, 3, 5, 9, 123, 5 });
arraysList.Add(new int[] { 3 });
arraysList.Add(new int[] { 9,8 });
ConcurrentBag<int> SummedValueOfEveryArray = new ConcurrentBag<int>();
Parallel.ForEach(arraysList, array =>
{
SummedValueOfEveryArray.Add(array.Sum());
});
//Your result
var result = SummedValueOfEveryArray.ToArray<int>();
//The sum of all arrays
var totalSum = SummedValueOfEveryArray.Sum();
This code will do what you ask. One side note however, this only parallelizes when .Net feels it could improve performance.
List<int[]> intlist = new List<int[]>();
int[] result = intlist.AsParallel().Select(arr => arr.Sum()).ToArray();
Given 1 to 4 arrays it may be that .Net never sees the point of parallelizing. But if you absolutely must you can force parallelization by using Parallel.For as shown below.
List<int[]> intlist = new List<int[]>();
int[] result = new int[intlist.Count];
Parallel.For(0, intlist.Count, i =>
{
result[i] = intlist[i].Sum();
});
If you had a List of arrays like:
List<int[]> ListOfArrays = new List<int[]>();
ListOfArrays.Add(new int[] { 1, 1 });
ListOfArrays.Add(new int[] { 2, 1 });
How would you find the index of { 2, 1} in the List?
I do not want to use an iteration loop. I would like a concise method like the one suggested by PaRiMaL RaJ in Check if string array exists in list of string:
list.Select(ar2 => arr.All(ar2.Contains)).FirstOrDefault();
(the above code will return true if members of a given string array exist in a list of string arrays)
var myArr = new int[] { 2, 1 };
List<int[]> ListOfArrays = new List<int[]>();
ListOfArrays.Add(new int[] { 1, 1 });
ListOfArrays.Add(new int[] { 4, 1 });
ListOfArrays.Add(new int[] { 1, 1 });
ListOfArrays.Add(new int[] { 2, 1 });
int index = ListOfArrays.FindIndex(l => Enumerable.SequenceEqual(myArr, l));
You can use the SequenceEqual method for this. See MSDN: https://msdn.microsoft.com/en-us/library/vstudio/bb348567(v=vs.100).aspx
You can try this:
List<int[]> ListOfArrays = new List<int[]>();
ListOfArrays.Add(new int[] { 1, 1 });
ListOfArrays.Add(new int[] { 2, 1 });
var chk = ListOfArrays.FindIndex(e => (e.SequenceEqual(new int[] { 2, 1 })));
I have 2D array in c#, like this:
int[][] 2darray = { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } };
how can I get one column as normal array, like
int[] array = 2darray[1][]; //example, not working
and have
int[] array = {3,4};
?
Thanks.
There are several reasons why your code can't compile
This way it works:
int[][] array2d = { new[]{ 1, 2 }, new[]{ 3, 4 }, new[]{ 5, 6 }, new[]{ 7, 8 } };
int[] array = array2d[0];
Problems:
2darray is not a valid variable name
The indexing is wrong
The initialization of the original array is wrong
EDIT:
As stated by #heltonbiker, if you require all elements of the first column, you can use this:
int[] col = array2d.Select(row => row[0]).ToArray();
For an array with two columns and four rows, you can use LINQ this way:
using System.Linq;
first_column = _2darray.Select(row => row[0]).ToArray();
Note that changing the first or second array will not change the other one.
You are confusing jagged arrays and multidimensional arrays in C#. While they are similar, there is a slight difference. Rows in a jagged array can have a different number of elements, while in a 2D-array they are of the same length. Therefore when working with jagged arrays you need to remember to write handling for a missing column element. I composed a sample console app below to show how both of them work - it uses 0 as a substitute for a missing element, but you can throw an error etc.:
using System.Collections.Generic;
namespace JaggedArrayExample
{
class Program
{
static void Main(string[] args)
{
//jagged array declaration
int[][] array1;
//jagged array declaration and assignment
var array2 = new int[][] {
new int[] { 1, 2 },
new int[] { 3, 4 },
new int[] { 5, 6 },
new int[] { 7, 8 }
};
//2D-array declaration
int[,] array3;
//2D-array declaration and assignment (implicit bounds)
var array4 = new int[,] {{1, 2}, {3, 4}, {5, 6}, {7, 8}};
//2D-array declaration and assignment (explicit bounds)
var array5 = new int[4, 2] {{1, 2}, {3, 4}, {5, 6}, {7, 8}};
//get rows and columns at index
var r = GetRow(array2, 1); //second row {3,4}
var c = GetColumn(array2, 1); //second column {2,4,6,8}
}
private static int[] GetRow(int[][] array, int index)
{
return array[index]; //retrieving the row is simple
}
private static int[] GetColumn(int[][] array, int index)
{
//but things get more interesting with columns
//especially if jagged arrays are involved
var retValue = new List<int>();
foreach (int[] r in array)
{
int ub = r.GetUpperBound(0);
if (ub >= index) //index within bounds
{
retValue.Add(r[index]);
}
else //index outside of bounds
{
retValue.Add(0); //default value?
//or you can throw an error
}
}
return retValue.ToArray();
}
}
}
try this, it should work
int[] array = array2d[1];
Change the name of the variable to array2d, you cannot have variable that starts with number, a variable can start with letter or underscore.
I am in the middle of converting C++ code to C#. I am having trouble with some C++ array static initialization. Consider the following piece of C++:
int Values[][32] = {
{}, {}, {1, 2, 3}, {1}
};
What this does is creates a matrix of 4x32 integers. I need to do same or similar in C# in as straightforward way as possible. I am looking to get either
static int[][] Values = {...};
...or
static int[,] Values = {...};
The thing is C# does not seem to allow array initialization with uneven sub-array sizes. Other than this, if one specifies new int[4,32] {...} then everything between curly braces must be of exactly 32 length. With C++ one can specify {1, 2, 3} and the compiler will fill in the rest of the missing array members with zeros.
[EDIT] I have tried using LINQ and got what I desire but it looks cumbersome.
In C# the size of your array initializer must match the declared size of the array. You do not need to declare the size if you would like to avoid duplication.
If you need all entries to be of the same size, you can do it with a little helper function Expand, like this:
static int[] Expand(int[] src, int size) {
var res = new int[size];
Array.Copy(src, res, src.Length);
return res;
}
static int[][] Values = new int[4][] {
Expand(new[] {1}, 32)
, Expand(new[] {1,2,3}, 32)
, Expand(new[] {1,2,3}, 32)
, Expand(new[] {1,2,3, 4, 5}, 32)
};
I deleted my previous answer and am adding another (less eloquent) one that should work.
// utility function you can put in a class
static int[] BuildArray32(params int[] values)
{
int[] retVal = new int[32];
Array.Copy(values, retVal, values.Length);
return retVal;
}
// array initializer code
int[][] Values = {
BuildArray32(),
BuildArray32(),
BuildArray32(1, 2, 3),
BuildArray32(1),
};
EDIT Or you could make a builder class :)
class MatrixBuilder
{
int width;
List<int[]> rows;
public MatrixBuilder(int width)
{
this.width = width;
this.rows = new List<int[]>();
}
public MatrixBuilder Add(params int[] row)
{
int[] wideRow = new int[width];
Array.Copy(row, wideRow, row.Length);
rows.Add(wideRow);
return this;
}
public int[][] ToMatrix()
{
return rows.ToArray();
}
}
int[][] Values2 = new MatrixBuilder(32)
.Add()
.Add()
.Add(1, 2, 3)
.Add(1)
.ToMatrix();
You can't do it in c#. you can either initialise the arrays all to zeros, then apply your known initial values afterwards:
int[][] initAll = new []
{
new int[32] ,
new int[32] ,
new int[32] ,
new int[32]
};
or initialize a jagged array:
int[][] initJagged = new[]
{
new[] {1, 3, 5, 7, 9},
new[] {1, 3, },
new[] {1, 3,0,0,0,0,},
new int[32]
};