CSharp - Array Multidimensional Arrays

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Introduction

Multidimensional arrays come in two varieties: rectangular and jagged.

Rectangular arrays are an n-dimensional block of memory, and jagged arrays are arrays of arrays.

Rectangular arrays

Rectangular arrays are declared using commas to separate each dimension.

The following declares a rectangular two-dimensional array, where the dimensions are 3 by 3: 

int[,] matrix = new int[3,3];

GetLength() method from array returns the length for a given dimension starting at 0. 

for (int i = 0; i < matrix.GetLength(0); i++){
    for (int j = 0; j < matrix.GetLength(1); j++){
         matrix[i,j] = i * 3 + j;
    }    
}

A rectangular array can be initialized as follows: 

int[,] matrix = new int[,]{
       {0,1,2},
       {3,4,5},
       {6,7,8}
};

Jagged arrays

Jagged arrays are declared using successive square brackets to represent each dimension.

The following code declares a jagged two-dimensional array, where the outermost dimension is 3: 

int[][] matrix = new int[3][];

Each inner array can be an arbitrary length and must be created manually: 

for (int i = 0; i < matrix.Length; i++)
{
       matrix[i] = new int[3];                    // Create inner array
       for (int j = 0; j < matrix[i].Length; j++)
         matrix[i][j] = i * 3 + j;
}

A jagged array can be initialized as follows. 

int[][] matrix = new int[][]
{
       new int[] {0,1,2},
       new int[] {3,4,5},
       new int[] {6,7,8,9}
};

Quiz

Example