All programs in this package are

  Copyright (c) 2005 Zeljko Vrba <zvrba@globalnet.hr>

  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:

  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Run make (GNU make required) to build the programs. Each program accepts
on the command-line a single argument: the name of the input file, and
prints solutions, separated by blank lines, on stdout. If no output is
produced, there is no solution (no special message is given in such case).

You can edit the Makefile and set CCADDFLAGS to optimizing flags, and/or
change the CC variable to set the compiler.

Sudoku solver
=============
The input format for this program is free-formed. Important characters in
the input are . (empty cell) and digits 0-9. There must be exactly 81 such
character. All other characters are IGNORED. This allows you to load puzzles
in the format as given on the following links:

http://angusj.com/sudoku/
http://angusj.com/sudoku/ss_undefined_2.zip

I can't reproduce these files in the distribution as they are copyrighted.
Some example inputs are su*.txt. su1.txt has 6 distinct solutions (so it's
not a "valid" sudoku puzzle, but the program can find all of them).
su2.txt is the "Daily Sudoku" (classic) from http://www.dailysudoku.com/
at the day 2005-12-31. su3.txt is taken from the http://act365.com/sudoku/
puzzle gallery, "Unsolvable" level.

Killer sudoku solver
====================
REGION is a set of cells having the sum specified in the puzzle. The first
element in the line is the region sum, while other elements are indices
of the cells contained in the region. Indices start from 0 at the top left
corner and increase to the right and bottom. See the following image:

    ----------------
    |0 |1 |2 |.....
    ----------------
    |9 |10|  |.....
    ---------------
    ....

NOTE! There must be no empty lines in the file, not even at the end of the
file. The program will report a file format error otherwise.

Files ks[1-4].txt correspond to gentle, moderate, tricky and tough puzzles
on the following URL:

http://www.timesonline.co.uk/article/0,,7-1757275,00.html

Take for example the tricky puzzle, and consider the L-shaped region in the
top-left subgrid that sums to 14: it is described by the following line:
14 9 18 19
| |
| +---> cells contained in the region
v
the region sum

Of course, the user interface leaves much to be desired :) This program is
more of an experiment of how feasible it is to use brute-force method on this
problem: very feasible. The tricky puzzle is solved in 0.09s on a 2GHz
Pentium M (when compiled with optimizations).

Kakuro solver
=============
http://www.kakuro.com/puzzles.php

The input is simpler than for the previous program. The first line must
contain the dimensions (rows and columns) of the puzzle, followed by cell
or run definitions. The definitions are in the following format:

0 1 2
56 0 0 7 2
49 3 2 21 6

The first line specifies indices of ALL unfillable cells. Constraint cells
MUST be omitted in this line.

The following lines specify one or two runs. Each line begins with the
constraint cell index, followed by two pairs of numbers. The first
pair of numbers is <SUM,SIZE> for the DOWN run, and the second pair of
numbers is <SUM,SIZE> for the RIGHT run. SIZE is in the number of
cells.

Files ka[1-6].txt are examples from http://www.kakuro.com/puzzles.php

If -test is given instead of the file name, it prints the nicely formatted
G_sum_table to show all possible sum combinations within the constraints
of the rules.

The program checks the input data for consistency. It will display a variety
of diagnostic messages. Here I just want to explain the ambiguity in the
following message kind:

overflowing (down?) run or misplaced constraint cell 78

The cause can be several reasons:
- overflowing down run starting at cell 78
- constraint cell misplaced in some other run
- NON-OBVIOUS: the previous point can be caused by overflowing previous down
  or right run so that it captures a constraint cell

Incompletely covered cell is a cell which is a member of only one run,
whereas an uncovered cell is not a member of any run (and was not declared
as uncoverable).