#lang racket
(define block-strings
(list "BO" "XK" "DQ" "CP" "NA"
"GT" "RE" "TG" "QD" "FS"
"JW" "HU" "VI" "AN" "OB"
"ER" "FS" "LY" "PC" "ZM"))
(define BLOCKS (map string->list block-strings))
(define (can-make-word? w)
(define (usable-block blocks word-char)
(for/first ((b (in-list blocks)) #:when (memf (curry char-ci=? word-char) b)) b))
(define (inner word-chars blocks tried-blocks)
(cond
[(null? word-chars) #t]
[(usable-block blocks (car word-chars))
=>
(lambda (b)
(or
(inner (cdr word-chars) (append tried-blocks (remove b blocks)) null)
(inner word-chars (remove b blocks) (cons b tried-blocks))))]
[else #f]))
(inner (string->list w) BLOCKS null))
(define WORD-LIST '("" "A" "BARK" "BOOK" "TREAT" "COMMON" "SQUAD" "CONFUSE"))
(define (report-word w)
(printf "Can we make: ~a? ~a~%"
(~s w #:min-width 9)
(if (can-make-word? w) "yes" "no")))
(module+ main
(for-each report-word WORD-LIST))
(module+ test
(require rackunit)
(check-true (can-make-word? ""))
(check-true (can-make-word? "A"))
(check-true (can-make-word? "BARK"))
(check-false (can-make-word? "BOOK"))
(check-true (can-make-word? "TREAT"))
(check-false (can-make-word? "COMMON"))
(check-true (can-make-word? "SQUAD"))
(check-true (can-make-word? "CONFUSE")))