code: static int closestCorner4(Grid g ) {
  		double bestDistance = g.get(0,0).center.normSq();
  		int bestIdx = 0;
  
  		double d = g.get(0,g.columns-1).center.normSq();
  		if( d < bestDistance ) {
  			bestDistance = d;
  			bestIdx = 3;
  		}
  		d = g.get(g.rows-1,g.columns-1).center.normSq();
  		if( d < bestDistance ) {
  			bestDistance = d;
  			bestIdx = 2;
  		}
  		d = g.get(g.rows-1,0).center.normSq();
  		if( d < bestDistance ) {
  			bestIdx = 1;
  		}
  
  		return bestIdx;
  	}
docs: Number of CCW rotations to put selected corner into the canonical location.  Only works
  when there are 4 possible solutions
  @param g The grid
  @return number of rotations