What is the difference between these two ways of declaring an array? [duplicate]

Question

What is the difference between:

int [][] myArray;

and

int [,] myOtherArray;

Answer 1

The first is a jagged array: an array where each item in the array is another array

int[][] jaggedArray = new int[3][];
jaggedArray[0] = new int[5];
jaggedArray[1] = new int[4];
jaggedArray[2] = new int[2];

The second is a multidimensional array, aka a matrix.

int[,] array = new int[4, 2]; // create a 4 by 2 matrix

Answer 2

myArray is a jagged array, or an array of arrays. Each element of myArray is itself an int[].

myOtherArray is a rectangular (or multidimensional) array - a single object containing all the data directly.

Which you should use really depends on the situation. Sometimes it can be handy to have an array for each "row" of data (with the ability to replace whole rows, and have rows with different lengths), whereas at other times it makes sense to force a uniform layout.