Problem Set 10 - UBC 2024 - CPSC 110

;; DO NOT PUT ANYTHING PERSONALLY IDENTIFYING BEYOND YOUR
CWL IN THIS FILE.
;; YOUR CWLs WILL BE SUFFICIENT TO IDENTIFY YOU AND, IF YOU HAVE
ONE, YOUR
;; PARTNER.
;;
(require spd/tags)

(@assignment psets/pset-10); Do not edit or remove this tag

;; If you are:
;; - A 110 or 107 student replace the first set of '???'s with your cwl.
;; For problem sets, If you have a partner, please replace the second
;; set of '???'s with their cwl. Remember this, it is what you will
;; do with these @cwl annotations for the whole course.
;; - A UBC Extended Learning student, replace the first set of ??? with
;; your email address as confirmed in the email you received from
;; extended learning. The handin password is also in that email.
;; Remember this, it is what you will do with these @cwl annotations
;; for the whole course.
;;
(@cwl ??? ???)


(@problem 1)
;;
;; Complete the design of the following function.
;;
;; Hint: sometimes for functions with accumulators it is useful for
;; the trampoline to deal with the special case of the empty
;; list or empty tree using an if expression.
;;

(@htdf max-num-repeats)
(@signature (listof String) -> Natural)
;; produce maximum number of times same string appears consecutively in los0
(check-expect (max-num-repeats empty) 0)
(check-expect (max-num-repeats (list "cat")) 1)
(check-expect (max-num-repeats (list "cat" "bird" "dog")) 1)
(check-expect (max-num-repeats (list "cat" "cat" "bird" "dog")) 2)
(check-expect (max-num-repeats (list "cat" "cat" "bird" "dog" "dog" "dog"))

, 3)
(check-expect (max-num-repeats (list "cat" "cat" "cat"
"bird"
"boy" "boy" "boy"
"toy" "toy" "toy" "toy" "toy"
"trick"
"zebra" "zebra" "zebra" "zebra"))
5)
(check-expect (max-num-repeats (list "dog" "cat" "bird"
"dog" "dog" "dog"
"moose" "dog"))
3)

(@template-origin (listof String) accumulator)

(define (max-num-repeats los)
;;current-string is String; the previous first string of the list
;;count is Natural; the number of times that current has been seen so far
;;rsf is Natural; the highest count so far

(local [(define (fn-for-los los current-string count rsf)
(cond [(empty? los) rsf]
[else
(if (string=? (first los) current-string)
(if (>= (add1 count) rsf)
(fn-for-los (rest los) (first los)
(add1 count) (add1 count))
(fn-for-los (rest los) (first los) (add1 count) rsf))
(fn-for-los (rest los) (first los) 1 rsf))]))]
(if (empty? los)
0
(fn-for-los los (first los) 0 1))))




(@problem 2)
;;
;; Complete the design of the following function.
;;
;; Your solution MUST BE TAIL RECURSIVE.
;;