#lang racket
(define (show-stem+leaf data)
  (define xs (sort data <))
  (for ([stem (add1 (floor (/ (last xs) 10)))])
    (printf "~a|" (~a #:width 2 #:align 'right stem))
    (for ([i xs])
      (define-values [q r] (quotient/remainder i 10))
      (when (= q stem) (printf " ~a" r)))
    (newline)))
(show-stem+leaf (sequence->list (in-producer read eof)))