December 1997 Programmer's Challenge

Clueless Crosswords

Mail solutions to: progchallenge@mactech.com
Due Date: 11:59pm EDT, Monday, 1 December 1997

Clueless Crosswords

 A couple of months ago, Bob Noll sent me a Challenge suggestion involving a crossword puzzle variant published by one of his local newspapers. The difficulty in using that suggestion was deciding how to provide the clues to the puzzle in a usable form. I thought about providing some sort of thesaurus, but giving simple synonyms as clues didn't seem to capture the crossword spirit. Then it occurred to me that clues serve only to make the crossword easy to solve, an advantage that certainly wouldn't be needed by our skilled Challenge readers or by the code they write. So the Challenge this month is to write code that will solve a crossword puzzle without clues.

The prototype for the code you should write is:

#define kMaxSize 32
typedef char Puzzle[kMaxSize][kMaxSize];

void Crossword(

Puzzle thePuzzle,   /* return solved puzzle here */
char *dictionary, /* array of words to choose from */
long puzzleSize,    /* number of rows/cols in puzzle */
long dictSize       /* number of words in dictionary */

);

Your Crossword routine will be provided with thePuzzle, where cell thePuzzle[row][col] will be initialized to a zero if you are to fill in that cell, or initialized to 0xFF if the cell is blacked out. The first puzzleSize rows and columns constitute the puzzle; the remaining cells in thePuzzle array are padding and should be ignored. You are to fill in the empty cells of thePuzzle with words from the dictionary provided, such that each uninterrupted sequence of blank cells, both horizontal and vertical, forms a word from the dictionary. The dictionary will contain all of the words needed to solve thePuzzle, but, to make things more interesting, it will also contain extra words not needed to solve thePuzzle. The dictionary may contain only a few extra words, or it may contain as many as 10 extra words for each word used in thePuzzle. Words in the dictionary are not guaranteed to be in any order, and any word might be used more than once in thePuzzle.

Each puzzle is guaranteed to have at least one solution using the dictionary provided. You will be guaranteed 20MB of memory for your code, static data, and any dynamically allocated memory. You may use more memory if it is available, but your code should detect and respond to memory allocation failures if you ask for more than the guaranteed amount of memory. As always, you must deallocate any dynamically allocated memory before returning.

This will be a native PowerPC Challenge, using the latest CodeWarrior environment. Solutions may be coded in C, C++, or Pascal. The Challenge winner will be the entry that provides a correct solution to a set of crossword puzzles in the minimum time. Thanks to Bob Noll for suggesting a crossword puzzle problem, he wins two Challenge points for the suggestion.