Celestin Apprentice 7/Apprentice-Release7.iso/Environments/Small Eiffel 0.4.8/lib_show/pyramid2.e

Text File | 1997-04-13 | 3KB | 168 lines

-- Part of SmallEiffel -- Read DISCLAIMER file -- Copyright (C)
-- Dominique COLNET and Suzanne COLLIN -- [e-mail]
--
class PYRAMID2
--
--| Auteur : Christophe Alexandre
--|  date  : Tue Feb 27 14:39:12 1996
--|
--| Run faster than pyramid.e

inherit ANY redefine print_on end;

creation {ANY}
   make

feature {NONE}

   pyramid: ARRAY2[INTEGER];

   used: ARRAY[BOOLEAN]; -- Already used numbers in `pyramid'.

   make is
      do
     from
        ask
     until
        io.last_integer > 1
     loop
        ask;
     end
     io.put_string("I am working...%N");
     fill(io.last_integer);
      end; -- make

   ask is
      do
     io.put_string("Size of the pyramid %
            % (a small number greater than 1) : ");
     io.read_integer;
     io.put_new_line;
      end; -- ask

   fill(size : INTEGER) is
     -- Fill in a `pyramid' of `size' elements.
      require
     size > 1;
      do
     !!used.make(1,(size+1)*size // 2);
     !!pyramid.make(1,size,1,size);
     if solution(1) then
        print_on(std_output)
     else
        io.put_string("Sorry I can't find a solution.%N");
     end;
      end; -- fill

   put(value,line,column: INTEGER) is
     -- Updtate `pyramid' and `used'.
      do
     used.put(true,value);
     pyramid.put(value,line,column);
      end; -- put

   remove(line,column :INTEGER) is
     -- Updtate `pyramid' and `used'.
      do
     if pyramid.item(line,column) /= 0 then
        used.put(false,pyramid.item(line,column));
        pyramid.put(0,line,column);
     end;
      end; -- remove

   solution(column:INTEGER): BOOLEAN is
     -- Search a solution using a back-tracking algorithm.
      local
     nb,i: INTEGER;
      do
     if column > pyramid.upper1 then
        Result := true;
     else
        from
           nb := used.upper
        until
           Result or nb = 0
        loop
           if not used.item(nb) then
          Result := fill_column(column,nb)
           end;
           if not Result then
          from
             i := pyramid.lower1
          until
             pyramid.item(i,column) = 0 or else i > pyramid.upper1
          loop
             remove(i,column);
             i := i + 1;
          end;
           end;
           nb := nb - 1;
        end;
     end;
      end; -- solution

   fill_column(col,val: INTEGER): BOOLEAN is
      local
     v, i: INTEGER;
      do
     from
        i := 2;
        put(val,1,col);
     until
        i > col or Result
     loop
        v := (pyramid.item(i-1,col-1)-pyramid.item(i-1,col)).abs
        if used.item(v) then
           Result := true;
        else
           put(v,i,col);
           i := i+1;
        end;
     end;
     if Result then
        from
        until
           i < used.lower
        loop
           remove(i,col);
           i := i-1;
        end;
        Result := false;
     else
        Result := solution(col+1);
     end;
      end; -- fill_column

   print_on(file: STD_FILE_WRITE) is
     -- display the pyramid to the standart output.
      local
     line,column : INTEGER;
     blanks : STRING;
      do
     from
        file.put_string("%NSolution found : %N");
        line := pyramid.lower1;
        !!blanks.make(0);
     until
        line > pyramid.upper1
     loop
        file.put_string(blanks);
        from
           column := pyramid.lower2
        until
           column > pyramid.upper2
        loop
           if pyramid.item(line,column) /= 0 then
          file.put_integer(pyramid.item(line,column));
          file.put_string(" ");
           end;
           column := column+1;
        end;
        file.put_new_line;
        line := line+1;
        blanks.add_last(' ');
     end;
      end; -- print_on

end -- PYRAMID2