Adding blank rows to a 2d array in Java
Here's a solution with ArrayLists: (test included)
int[][] ar = new int[][]
{
{ 0, 1, 2 },
{ 3, 4, 5 },
{ 6, 7, 8 } };
ArrayList<ArrayList<Integer>> a = new ArrayList<>(ar.length);
ArrayList<Integer> blankLine = new ArrayList<>(ar.length * 2 - 1);
for (int i = 0; i < ar.length * 2 - 1; i++)
{
blankLine.add(0);
}
for (int i = 0; i < ar.length; i++)
{
ArrayList<Integer> line = new ArrayList<>();
for (int j = 0; j < ar[i].length; j++)
{
line.add(ar[i][j]);
if (j != ar[i].length - 1)
line.add(0);
}
a.add(line);
if (i != ar.length - 1)
a.add(blankLine);
}
for (ArrayList<Integer> b : a)
{
System.out.println(b);
}
Output:
[0, 0, 1, 0, 2]
[0, 0, 0, 0, 0]
[3, 0, 4, 0, 5]
[0, 0, 0, 0, 0]
[6, 0, 7, 0, 8]
nobillygreen
Updated on June 04, 2022Comments
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nobillygreen almost 2 years
Say I have the following 2d array in Java set to a variable named myMap:
1 3 1 3 2 3 1 3 1
The next step in my program is to add rows and columns of zeros as follows:
1 0 3 0 1 0 0 0 0 0 3 0 2 0 3 0 0 0 0 0 1 0 3 0 1
Basically, I'm adding arrays of zero into the spaces between the previous rows/columns. I then fill them in with appropriate numbers (irrelevant to my question) and repeat the process (adding more rows/columns of zeros) a finite number of times.
My question is as follows- what is the easiest and most efficient way to do this in Java? I know I could create a new 2d array and copy everything over, but I feel like there may be a more efficient way to do this. My intuition says that a 2d ArrayList may be the better way to go.
Also, and this my be important, when my program begins, I DO know what the maximum size this 2d array. Also, I cannot expect the symmetry of the numbers that I put in for this example (these were just put in for a good visual reference).
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nobillygreen over 11 yearsThis is beautiful! Thank you so much for the help, Ryan!