Jagged arrays

Learn flexible row structures with arrays of arrays (jagged).

Jagged arrays

An array whose rows may have different sizes is called a jagged array. Its type is int[][]; literally 'array of arrays'. int[][] rows = new int[3][]; creates a jagged array with three rows.

Each row is a separate array; for example rows[0] = new int[] { 1, 2 }; makes the first row two elements. int[,] keeps every row the same size, while int[][] allows flexible row lengths.

Jagged initialization and access

You can also initialize a jagged array in one line: int[][] rows = { new int[] { 1, 2 }, new int[] { 3, 4, 5 } };. The first row has two, the second three elements.

Access uses two separate brackets: rows[1][2] gives the second row's third element. rows.Length is the row count and rows[i].Length the length of row i.

Exercise Declare a jagged array and print a cell

Declare a jagged array rows with the value { new int[] { 1, 2 }, new int[] { 3, 4, 5 } }. Then print rows[1][2] with Console.WriteLine. The output should be 5.

Show example solution

Write int[][] rows = { new int[] { 1, 2 }, new int[] { 3, 4, 5 } }; and print it with Console.WriteLine(rows[1][2]);
Example solution:
using System;

class Program
{
    static void Main()
    {
        int[][] rows = { new int[] { 1, 2 }, new int[] { 3, 4, 5 } };
        Console.WriteLine(rows[1][2]);
    }
}

Test yourself

Write the jagged array type

int____ rows = new int[3][];

Show answer

int[][] rows = new int[3][];

Match each type to its meaning

int[][]

Jagged array
int[,]

Matrix (rectangular)
new int[3][]

Three-row jagged
rows[0]

First row array
Which is a jagged array (rows of different sizes)?
```
// which one?
```
- int[,] m
- int[] nums
- int[][] rows
- int n
Show answer

int[][] rows — Correct. int[][] is an 'array of arrays' where each row may have a different size.

Next lesson: Summary - Arrays

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