Nonogram solver
Each row and column of a rectangular grid is annotated with the lengths of its distinct runs of occupied cells. Using only these lengths you should find one valid configuration of empty and occupied cells (or show a failure message):
Problem: Solution: . . . . . . . . 3 . # # # . . . . 3 . . . . . . . . 2 1 # # . # . . . . 2 1 . . . . . . . . 3 2 . # # # . . # # 3 2 . . . . . . . . 2 2 . . # # . . # # 2 2 . . . . . . . . 6 . . # # # # # # 6 . . . . . . . . 1 5 # . # # # # # . 1 5 . . . . . . . . 6 # # # # # # . . 6 . . . . . . . . 1 . . . . # . . . 1 . . . . . . . . 2 . . . # # . . . 2 1 3 1 7 5 3 4 3 1 3 1 7 5 3 4 3 2 1 5 1 2 1 5 1
The problem above could be represented by two lists of lists:
X = [[3], [2,1], [3,2], [2,2], [6], [1,5], [6], [1], [2]] Y = [[1,2], [3,1], [1,5], [7,1], [5], [3], [4], [3]]
A more compact representation of the same problem uses strings, where the letters represent the numbers, A=1, B=2, etc:
x = "C BA CB BB F AE F A B" y = "AB CA AE GA E C D C"
For this task try to solve the problems read from a "nonogram_problems.txt" file, copied from this:
C BA CB BB F AE F A B AB CA AE GA E C D C F CAC ACAC CN AAA AABB EBB EAA ECCC HCCC D D AE CD AE A DA BBB CC AAB BAA AAB DA AAB AAA BAB AAA CD BBA DA CA BDA ACC BD CCAC CBBAC BBBBB BAABAA ABAD AABB BBH BBBD ABBAAA CCEA AACAAB BCACC ACBH DCH ADBE ADBB DBE ECE DAA DB CC BC CAC CBAB BDD CDBDE BEBDF ADCDFA DCCFB DBCFC ABDBA BBF AAF BADB DBF AAAAD BDG CEF CBDB BBB FC E BCB BEA BH BEK AABAF ABAC BAA BFB OD JH BADCF Q Q R AN AAN EI H G E CB BAB AAA AAA AC BB ACC ACCA AGB AIA AJ AJ ACE AH BAF CAG DAG FAH FJ GJ ADK ABK BL CM
This task is the problem n.98 of the "99 Prolog Problems" by Werner Hett (also thanks to Paul Singleton for the idea and the examples):
https://sites.google.com/site/prologsite/prolog-problems
Some Haskell solutions:
http://www.haskell.org/haskellwiki/99_questions/Solutions/98
Bonus Problem: generate nonograms with unique solutions, of desired height and width.