consistent need to traverse a multidimensional matrix

[blissful garnet]

So I posted here a few days ago about having trouble with matrixes. My exam is going to focus heavily on matrixes and manipulation of them. One thing i'm particularly hitting a wall with is making sure I don't get out of bound errors when traversing a matrix. I know how to access the rows and columns of a matrix, but when needing to traverse a matrix in an unfamiliar order I get lost. One assignment wants me to traverse a matrix diagonally. Here is an example of a question that may be similar to what I am asked.

Given a two-dimensional array arr with dimensions MxN (M and N are not necessarily the same), you are
asked to write a method called flatten that will create and return a one-dimensional array based on arr
using the following scheme: only positive values from arr are kept and they are stored in the new one-
dimensional array sequentially, row-by-row. For example, with the following 3x4 array as input your method
should return the one-dimensional array also shown below. The original array should obviously remain intact.

[rain stirrup]

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[nocturne dawn]

ok so regarding avoiding out of bounds errors, try making sure you are using simple for loops for iteration and don't modify the variables inside the loop

e.g.

for(int i=0;i<yourMatrix.length;i++){
  for(int j=0;j<yourMatrix[i].length;j++){
    System.out.println(yourMatrix[i][j];
  }
}

In here, I am using i with yourMatrix and i is only used for that

similarly, j is used with yourMatrix[i] and not in different contexts

make sure that the condition and the access match

and if you are doing things with the diagonal, you might want to use Math.min

e.g.

//print all elements on the main diagonal
if(yourMatrix.length>0){
  for(int i=0;i<Math.min(yourMatrix.length,yourMatrix[0].length);i++){
    System.out.println(yourMatrix[i][i]);//assumes rectangular array
  }
}

or alternatively, you could do the same thing like this:

for(int i=0;i<yourMatrix.length;i++){
  if(i<yourMatrix[i].length){
    System.out.println(yourMatrix[i][i]);//assumes rectangular array
  }
}

essentially make sure you are checking dimensions before accessing them

[blissful garnet]

hm

okay well

i also need to be able to traverse back up

that is another big part of the problem

some of the problems involve needing to check if there is a bound at that index and then traversing back up if not