public int eval(INode state){
  SmallPuzzle tp=(SmallPuzzle)state;
  int diff=Math.abs(target[0] - tp.s[0]) + Math.abs(target[1] - tp.s[1]);
  if (tp.s[0] > target[0]) {
    diff*=2;
  }
  if (tp.s[1] > target[1]) {
    diff*=2;
  }
  return diff;
}

public int eval ( INode state ) { SmallPuzzle tp = ( SmallPuzzle ) state ; int diff = Math . abs ( target [ 0 ] - tp . s [ 0 ] ) + Math . abs ( target [ 1 ] - tp . s [ 1 ] ) ; if ( tp . s [ 0 ] > target [ 0 ] ) { diff *= 2 ; } if ( tp . s [ 1 ] > target [ 1 ] ) { diff *= 2 ; } return diff ; }
evaluate how far from the solution state is .
