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///////////////////////////////////////////////////////////////////////////////
// Lisaac Example //
// //
// LSIIT - ULP - CNRS - INRIA - FRANCE //
// //
// This program is free software: you can redistribute it and/or modify //
// it under the terms of the GNU General Public License as published by //
// the Free Software Foundation, either version 3 of the License, or //
// (at your option) any later version. //
// //
// This program is distributed in the hope that it will be useful, //
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
// GNU General Public License for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
// //
// http://isaacproject.u-strasbg.fr/ //
///////////////////////////////////////////////////////////////////////////////
Section Header
+ name := PYRAMID2;
- author := "Sonntag Benoit (bsonntag@loria.fr)";
- comment := "Run faster than pyramid.e";
Section Inherit
- parent_object:OBJECT := OBJECT;
Section Private
+ pyramid:ARRAY2[INTEGER];
+ used:ARRAY[BOOLEAN]; // Already used numbers in `pyramid'.
- fill size:INTEGER <-
// Fill in a `pyramid' of `size' elements.
(
? {size > 1};
used := ARRAY[BOOLEAN].create 1 to ((size+1) * size / 2);
pyramid := ARRAY2[INTEGER].create (1,1) to (size,size);
(solution 1).if {
print;
} else {
"Sorry I can't find a solution.\n".print;
};
);
- put value:INTEGER to (line,column:INTEGER) <-
// Updtate `pyramid' and `used'.
(
used.put TRUE to value;
pyramid.put value to (line,column);
);
- remove (line,column:INTEGER) <-
// Updtate `pyramid' and `used'.
(
(pyramid.item (line,column) != 0).if {
used.put FALSE to (pyramid.item (line,column));
pyramid.put 0 to (line,column);
};
);
- solution column:INTEGER :BOOLEAN <-
// Search a solution using a back-tracking algorithm.
( + nb,i:INTEGER;
+ result:BOOLEAN;
(column > pyramid.upper1).if {
result := TRUE;
} else {
nb := used.upper;
{ result | (nb = 0)}.until_do {
(! used.item nb).if {
result := fill_column column with nb;
};
(! result).if {
i := pyramid.lower1;
{(pyramid.item (i,column) = 0) || { i > pyramid.upper1 }}.until_do {
remove (i,column);
i := i + 1;
};
};
nb := nb - 1;
};
};
result
);
- fill_column col:INTEGER with val:INTEGER :BOOLEAN <-
( + v,i:INTEGER;
+ result:BOOLEAN;
i := 2;
put val to (1,col);
{(i > col) | result}.until_do {
v := (pyramid.item ((i-1),(col-1)) - pyramid.item ((i-1),col)).abs;
(used.item v).if {
result := TRUE;
} else {
put v to (i,col);
i := i + 1;
};
};
result.if {
{i < used.lower}.until_do {
remove (i,col);
i := i-1;
};
result := FALSE;
} else {
result := solution (col+1);
};
result
);
- print <-
// Display the pyramid to the standart output.
( + blanks:STRING;
"\nSolution found : \n".print;
blanks := STRING.create 10;
pyramid.lower1.to (pyramid.upper1) do { line:INTEGER;
blanks.print;
pyramid.lower2.to (pyramid.upper2) do { column:INTEGER;
(pyramid.item (line,column) != 0).if {
pyramid.item (line,column).print;
' '.print;
};
};
'\n'.print;
blanks.add_last ' ';
};
);
Section Public
- main <-
( + size: INTEGER;
// Read argument.
(COMMAND_LINE.upper = 0).if {
"Size of the pyramid (a small number greater than 1) : ".print;
IO.read_integer;
size := IO.last_integer;
} else {
size := COMMAND_LINE.item 1.to_integer;
};
"I am working...\n".print;
fill size;
);
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