C# - Jagged Arrays

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A Jagged array is an array of arrays, meaning that the elements of a jagged array are arrays themselves. Unlike a multidimensional array, a jagged array can contain an array of different lengths. You can declare a jagged array named 'scores' of type int as follows −

Jagged Arrays Declaration

You can declare a jagged array by specifying the number of rows, but the columns can vary for each row.

int [][] scores;

Declaring an array does not allocate space for it in memory. To create the array, you need to follow the syntax below −

int[][] scores = new int[5][];
for (int i = 0; i < scores.Length; i++) {
   scores[i] = new int[4];
}

Jagged Arrays Initialization

A jagged array can be initialized by providing values for each row individually, the number of elements can be different in each row.

You can initialize a jagged array as follows −

int[][] scores = new int[2][]  
{  
    new int[] { 92, 93, 94 },  
    new int[] { 85, 66, 87, 88 }  
};

Here:

• scores is a jagged array containing two arrays of integers.
• scores[0] is an array of 3 integers: { 92, 93, 94 }.
• scores[1] is an array of 4 integers: { 85, 66, 87, 88 }.

Example of a C# Jagged Array

The following example demonstrates how to declare, initialize, and print elements of a jagged array:

using System;

namespace ArrayApplication {
   class MyArray {
      static void Main(string[] args) {
         
         /* a jagged array of 5 array of integers*/
         int[][] a = new int[][]{new int[]{0,0},new int[]{1,2},
            new int[]{2,4},new int[]{ 3, 6 }, new int[]{ 4, 8 } };
         int i, j;
         
         /* output each array element's value */
         for (i = 0; i < 5; i++) {
            for (j = 0; j < 2; j++) {
               Console.WriteLine("a[{0}][{1}] = {2}", i, j, a[i][j]);
            }
         }
         Console.ReadKey();
      }
   }
}

When executed, this program outputs:

a[0][0]: 0
a[0][1]: 0
a[1][0]: 1
a[1][1]: 2
a[2][0]: 2
a[2][1]: 4
a[3][0]: 3
a[3][1]: 6
a[4][0]: 4
a[4][1]: 8

Iterating Over a Jagged Array

You can iterate over a jagged array using either a for loop or a foreach loop.

Example: Using a for Loop

In the following example, we use a for loop to iterate over a jagged array and display its elements:

using System;

class Program
{
    static void Main()
    {
        int[][] jaggedArray = new int[][]
        {
            new int[] {1, 2, 3},
            new int[] {4, 5},
            new int[] {6, 7, 8, 9}
        };

        for (int i = 0; i < jaggedArray.Length; i++)
        {
            for (int j = 0; j < jaggedArray[i].Length; j++)
            {
                Console.Write(jaggedArray[i][j] + " ");
            }
            Console.WriteLine();
        }
    }
}

When the above code is compiled and executed, it produces the following result −

1 2 3 
4 5 
6 7 8 9

Example: Using a foreach Loop

In the following example, we use a foreach loop to iterate over a jagged array and display its elements:

using System;

class Program
{
    static void Main()
    {
        int[][] jaggedArray = new int[][]
        {
            new int[] {1, 2, 3},
            new int[] {4, 5},
            new int[] {6, 7, 8, 9}
        };

        foreach (int[] array in jaggedArray)
        {
            foreach (int num in array)
            {
                Console.Write(num + " ");
            }
            Console.WriteLine();
        }
    }
}

When the above code is compiled and executed, it produces the following result −

1 2 3 
4 5 
6 7 8 9

Jagged Arrays vs. Multi-Dimensional Arrays

The following table shows the key differences between jagged arrays and multi-dimensional arrays: