0816-ambiguous-coordinates.rkt

#lang racket

(define (x-str str)
  (map (curry substring str 0) (range 1 (string-length str))))

(define (y-str str)
  (map (curry substring str) (range 1 (string-length str))))

(define (all-xy-pairs str)
  (if (= (string-length str) 1)
      str
      (map list (x-str str) (y-str str))))

(define (whole-str str)
  (map (curry substring str 0) (range 1 (add1 (string-length str)))))

(define (decimal-str str)
  (map (curry substring str) (range 1 (add1 (string-length str)))))

(define (all-wd-pairs str)
  (map list (whole-str str) (decimal-str str)))

; (define (whole-valid? str)
;   (cond [(= (string-length str) 1) true]
;         [(eq? (first (string->list str)) #\0) false]
;         [else true]))

(define (whole-valid? str)
  (or (= (string-length str) 1)
      (not (string-prefix? str "0"))))

(define (decimal-valid? str)
  (or (zero? (string-length str))
      (not (string-suffix? str "0"))))

(define (wd-pair-valid? wd-pair)
  (let ([whole (car wd-pair)]
        [decimal (cadr wd-pair)])
    (and (whole-valid? whole)
         (decimal-valid? decimal))))

(define (wd-pair->str wd-pair)
  (let ([whole (car wd-pair)]
        [decimal (cadr wd-pair)])
    (if (zero? (string-length decimal))
        whole
        (string-append whole "." decimal))))

(define (valid-wd-pairs str)
  (filter wd-pair-valid?
          (all-wd-pairs str)))

(define (valid-nums str)
  (map wd-pair->str
       (valid-wd-pairs str)))

(define (valid-xy-pairs str)
  (map (curry map valid-nums) (all-xy-pairs str)))

; (define (all-cons xy)
;   (let ([x-list (car xy)]
;         [y-list (cadr xy)])
;     (append-map (lambda (x)
;                   (map (lambda (y)
;                          (string-append "(" x ", " y ")"))
;                        y-list))
;                 x-list)))

(define (all-cons xy-pair)
  (let ([x-list (car xy-pair)]
        [y-list (cadr xy-pair)])
    (map (curryr string-join ", "
                 #:before-first "("
                 #:after-last ")")
         (cartesian-product x-list y-list))))

(define/contract (ambiguous-coordinates s)
  (-> string? (listof string?))
  (append-map all-cons
              (valid-xy-pairs (substring s 1 (sub1 (string-length s))))))

; (define xy (caddr (valid-xy "123456")))
; (define x-list (car xy))
; (define y-list (cadr xy))

(all-wd-pairs "123")
(valid-wd-pairs "123")
(valid-nums "123")
(all-xy-pairs "123")
(valid-xy-pairs "123")

(define str "123")

(ambiguous-coordinates "(123)")