You have a matrix...

private int[][] myMatrix;

each cell will only contain 0 or 1.

You need to find which columns and which rows contain at least one 1. i.e. 'cols 3,6 and 9 have at least one 1 and rows 2,7 and 10 have at least one 1'

I ran into this one about two years ago during an interview and they were trying to trip me up I am sure...the obvious (psudocode)
for ( int row = 0 ; row < myMatrix.length ; col++ ) {
for ( int col = 0 ; col < myMatrix[row].length ; col++ ) {
if ( myMatrix[row][col] == 1 ) {
'save row is some result set and save col is some other result set';
}
}
print the two result sets;

I am sure this is not the answer unless they were just trying to see if I know how to iterate a 2 dim array. There must be some clever algorithm that is very fast for this.