Array processing, shapes - arrays

Question

I have a square 2d array of values, where each row is identical, and where each element of row is one bigger than the last. For example:
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
I want to filter them, such that I can make a diamond as such:
1
1 2 3
1 2 3 4 5
1 2 3 4 5 6 7
1 2 3 4 5
1 2 3
1
Notice how the first part of the array is used, no matter how many elements are to be printed on that line. Also, spacing doesn't matter. I spaced them to show the diamond.
I know how to filter the top right "chunk" out, using j-i<(j/2). This will convert the original square into:
1
1 2 3
1 2 3 4 5
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7
How can I get the bottom right "chunk" to filter out also? What additional condition can I impose on the values?

Answer 1

Presuming you have found out and stored the length of the "side" of the square already then you could use something like below. However, if your square has an even length then it will not work (can't produce a diamond in this way from an even side length square).
The following is pseudo-code so you will need to adapt it for your language. I've also used 0-indexed arrays and presumed square is a 2D array.
for (i=0, i<length, i++)
{
for (j=0, j<Length, j++)
{
if (i < length/2)
{
if (j < length/2 AND j <= i)
print square[i][j]
}
}
else
{
if (j < length/2 AND j <= (length - i))
{
print square[i][j]
}
}
}
print newline
}