question: @ Override public Trie optimize ( Trie orig ) { List < CharSequence > cmds = orig . cmds ; List < Row > rows = new ArrayList < > ( ) ; List < Row > orows = orig . rows ; int remap [ ] = new int [ orows . size ( ) ] ; for ( int j = orows . size ( ) - 1 ; j >= 0 ; j -- ) { Row now = new Remap ( orows . get ( j ) , remap ) ; boolean merged = false ; for ( int i = 0 ; i < rows . size ( ) ; i ++ ) { Row q = merge ( now , rows . get ( i ) ) ; if ( q != null ) { rows . set ( i , q ) ; merged = true ; remap [ j ] = i ; break ; } } if ( merged == false ) { remap [ j ] = rows . size ( ) ; rows . add ( now ) ; } } int root = remap [ orig . root ] ; Arrays . fill ( remap , - 1 ) ; rows = removeGaps ( root , rows , new ArrayList < Row > ( ) , remap ) ; return new Trie ( orig . forward , remap [ root ] , cmds , rows ) ; }
target:  Optimize (remove empty rows) from the given Trie and return the resulting Trie.