Mirror half of a N x N adjacency matrix in Javascript

Question

I have half of an N x N matrix in a javascript array of arrays, and i need to get this half and "mirror" it on the other side of the main diagonal.

Here is an image that explains better:

The main diagonal is the red line, and i have the upper half of the matrix that needs to be "placed" below the red line too, forming a full matrix.

The data structure is something like this:

var map = [ ["0","1","2","3"], ["0", "1", "2"], ["0","1"], ["0"] ];

Lines with columns inside.

I often insert things i already tried in my questions, but in this time i couldn't even find out how to start. So, my apologize if i am not providing some more info.

Answer 1

One way to do it is something like this

var i = 0;
var j = 0;
var map = [ ["0","1","2","3"], ["0", "1", "2"], ["0","1"], ["0"] ];
var n = map.length;
var res = new Array(n);

for (i = 0; i < n; i++) {
  res[i] = new Array(n);
  for (j = 0; j < n - i; j++) {
    res[i][i+j] = map[i][j];
  }
}

for (i = 0; i < n; i++) {
  for (j = i + 1; j < n; j++) {
    res[j][i] = res[i][j];
  }
}

res will contain the mirrored array