What are common errors when working with two-dimensional arrays?

Common errors when working with two-dimensional arrays include out-of-bounds errors, incorrect initialisation, and improper iteration.

Out-of-bounds errors are one of the most common mistakes made when working with two-dimensional arrays. This error occurs when you try to access an element at an index that does not exist in the array. For example, if you have a 2D array of size 5x5, and you try to access the element at position [5][5], you will get an out-of-bounds error because the indices of the array only go up to 4 (since array indices start at 0).

Incorrect initialisation is another common error. When you declare a two-dimensional array, you need to specify the size of both dimensions. If you only specify the size of one dimension, or if you specify the sizes incorrectly, you will encounter errors. For instance, if you declare an array as int[][] array = new int[5][], you will get a null pointer exception when you try to access an element because the second dimension of the array has not been initialised.

Improper iteration over a two-dimensional array can also lead to errors. When iterating over a 2D array, you need to use nested loops - one loop for the rows and another for the columns. If you only use one loop, or if you use the loops in the wrong order, you will not be able to access all the elements in the array. For example, if you have a 2D array of size 5x5 and you only use one loop to iterate over it, you will only be able to access the first row of the array.

In addition, it's important to remember that two-dimensional arrays in programming languages like Java are actually arrays of arrays, and each row can potentially have a different length. This can lead to unexpected results if you assume that all rows have the same length. For example, if you create a 2D array where the first row has 5 elements and the second row has 3 elements, and you try to access the element at position [1][4], you will get an out-of-bounds error because the second row only has 3 elements.