Solving diagramless crossword puzzles

An interesting computational challenge is posed by finding the diagram in diagramless crossword puzzles. We describe two approaches to placing the words in the diagram to form a crossword puzzle, given the “across” and the “down” words. One algorithm systematically tries the possibilities. By discarding partially completed puzzles the solutions for large puzzles can be found in a reasonable amount of time. The second algorithm uses on intelligent search strategy building up the diagram word-by-word. Both methods were programmed in Modula-3, a strongly-typed, object-oriented language. We describe the programs and analyze their performance on a SPARC computer