How to make a Jagged Array?

Question

Thinking like a simple array:

Console.WriteLine("Number: ");
int x = Convert.ToInt32(Console.ReadLine());

string[] strA = new string[x];

strA[0] = "Hello";
strA[1] = "World";    

for(int i = 0;i < x;i++)
{
    Console.WriteLine(strA[i]);
}

Now, how can I do it with a double array?

I've already tried this:

Console.WriteLine("Number 1: ");
int x = Convert.ToInt32(Console.ReadLine());

Console.WriteLine("Number 2: ");
int y = Convert.ToInt32(Console.ReadLine());

// Got an error, right way string[x][];
// But how can I define the second array?
string[][] strA = new string[x][y]; 

strA[0][0] = "Hello";
strA[0][1] = "World";
strA[1][0] = "Thanks";
strA[1][1] = "Guys"; 

for(int i = 0;i < x;i++)
{
    for(int j = 0;i < y;i++)
    {
        // How can I see the items?
        Console.WriteLine(strA[i][j]); 
    }
}

If's there's a simpler way of doing this, i'll be happy to learn it.

It's only for knowledge, I'm studying double array for the first time, so have patience please :)

Here's my example: https://dotnetfiddle.net/PQblXH

Answer 1

You are working with jagged array (i.e. array of array string[][]), not 2D one (which is string[,])

If you want to hardcode:

  string[][] strA = new string[][] { // array of array
    new string[] {"Hello", "World"}, // 1st line 
    new string[] {"Thanks", "Guys"}, // 2nd line
  };

in case you want to provide x and y:

  string[][] strA = Enumerable
    .Range(0, y)                   // y lines
    .Select(line => new string[x]) // each line - array of x items
    .ToArray(); 

Finally, if we want to initialize strA without Linq but good all for loop (unlike 2d array, jagged array can contain inner arrays of different lengths):

  // strA is array of size "y" os string arrays (i.e. we have "y" lines)
  string[][] strA = new string[y][];

  // each array within strA
  for (int i = 0; i < y; ++i)
    strA[i] = new string[x]; // is an array of size "x" (each line of "x" items)

Edit: Let's print out jagged array line after line:

Good old for loops

  for (int i = 0; i < strA.Length; ++i) {
    Console.WriteLine();

    // please, note that each line can have its own length
    string[] line = strA[i];

    for (int j = 0; j < line.Length; ++j) {
      Console.Write(line[j]); // or strA[i][j]
      Console.Write(' ');     // delimiter, let it be space
    }
  } 

Compact code:

  Console.Write(string.Join(Environment.newLine, strA
    .Select(line => string.Join(" ", line))));

Answer 2

You're using a jagged array instead of a multidimensional one. Simply use [,] instead of [][]. You can then use it with new string[x, y].

Answer 3

First you need to clarify thing in your head before writing code.
I will recommend writing in simple phrase what you want to do. The code in your fiddle go into every direction. I will address the code in the fiddle and not your questionas you have typo error and other issue that where not present in the fiddle while the fiddle has error that the question do not have.

To simplify the problem lets use clear understandable names. The 2d array will be an table, with rows and columns.

//  1/. Ask for 2table dim sizes.
Console.WriteLine("Enter number of rows:");
var x = int.Parse(Console.ReadLine());
Console.WriteLine("Enter number of columns:");
var y = int.Parse(Console.ReadLine());

var table = new string[x, y];

You need to to declare your table before knowing its size.

// 2/. Fill the board
for (int row = 0; row < table.GetLength(0); row++)
{
    for (int col = 0; col < table.GetLength(1); col++)
    {
        Console.WriteLine($"Enter the value of the cell [{row},{col}]");
        table[row, col] = Console.ReadLine();
    }
}

table.GetLength(0) is equivalent to X, and table.GetLength(1) is equivalent to Y, and can be replace.

// 3/. Display the Table 
Console.Write("\n");
for (int row = 0; row < table.GetLength(0); row++)
{
    for (int col = 0; col < table.GetLength(1); col++)
    {
        Console.Write(table[row, col]);
    }
    Console.Write("\n");
}

For a 3x3 table with 00X, 0X0, X00 as inputs the result is

00X
0X0
X00

It works. You separate each cell when we display by simply adding a comma or a space. Fiddle

And for Jagged Array:

//  1/. Ask for 2table dim sizes.
Console.WriteLine("Enter number of rows:");
var x = int.Parse(Console.ReadLine());

var table = new string[x][];

// 2/. Fill the board
for (int row = 0; row < table.GetLength(0); row++)
{
    Console.WriteLine($"Enter of the line n°{row}");
    var lineSize = int.Parse(Console.ReadLine());
    table[row] = new string[lineSize];
    for (int col = 0; col < table[row].Length; col++)
    {
        Console.WriteLine($"Enter the value of the cell [{row},{col}]");
        table[row][col] = Console.ReadLine();
    }
    Console.Write("\n");
}

// 3/. Display the Table 
Console.Write("\n");
for (int row = 0; row < table.Length; row++)
{
    for (int col = 0; col < table[row].Length; col++)
    {
        Console.Write(table[row][col]);
    }
    Console.Write("\n");
}

Answer 4

Wrong variable in use:

for(int j = 0;i < y;i++) <- Should be j
{
    // How can I see the items?
    Console.WriteLine(strA[i][j]); 
}