question: public int eval ( INode state ) { TinyPuzzle tp = ( TinyPuzzle ) state ; if ( tp . s [ 0 ] > target [ 0 ] ) return Integer . MAX_VALUE ; if ( tp . s [ 1 ] > target [ 1 ] ) return Integer . MAX_VALUE ; return Math . abs ( target [ 0 ] - tp . s [ 0 ] ) + Math . abs ( target [ 1 ] - tp . s [ 1 ] ) ; }
target:  Evaluate how far from the solution state is. 