Racket while循环
Problem: 1805. 字符串中不同整数的数目
lc题解地址
思路
-
函数式编程？那是啥？有
set!和hash-set!好用吗 -
开始那一堆是在实现while break continue.按照racket文档里说的，你
(require dyoo-while-loop)也行。
？我require不了，leetcode没加载这个collection ，你应该去这个仓库把代码直接拉过来 -
简单的语法还是问gptchat吧。不然你和我一样分不清{make-hash,make-hasheq,make-hasheqv,make-hashalw}的区别。
-
(string=? "0" (substring word p1 (+ p1 1)))判断字符串某个下标的字符是不是字符'0'，你应该这么写。其他写法可能行。 -
chatgpt基本上不会写racket程序，超过5行就别指望简单改改能运行起来；但是chatgpt具备将java代码改写成scala代码的能力，我把
class改成object就过了这道leetcode题目 -
chatgpt将热门语言彼此做改写没什么问题的。2023-03-05将本次周赛t3t4的AC的java代码交给chatgpt改写为scala代码，只需要把“class”改为“object”提交就能过题。
-
以后简单的业务开发，可能交给专门写prompt的人员了。（x
代码
(require (for-syntax racket/base)
racket/stxparam)
(provide while break continue)
;; The following is adapted from:
;;
;; http://matt.might.net/articles/implementing-exceptions/
;;
;; with a few adjustments so that break and continue are
;; hygienic, and the extent of the break and continue are
;; around the body.
;;
(define-syntax-parameter break
(lambda (stx)
(raise-syntax-error #f "Used outside the context of a while body" stx)))
(define-syntax-parameter continue
(lambda (stx)
(raise-syntax-error #f "Used outside the context of a while body" stx)))
;; This enforces the use of break and continue:
;; you have to use them with parens, or else they should
;; complain at compile time.
(define-for-syntax (force-use-with-parens b)
(lambda (stx)
(syntax-case stx ()
[(_)
(with-syntax ([b b])
(syntax/loc stx
(b)))]
[(kw arg arg-rest ...)
(raise-syntax-error #f
(format "Must be directly used without arguments [e.g: (~a)]"
(syntax->datum #'kw))
stx
#'arg)]
[_
(identifier? stx)
(raise-syntax-error #f
(format "Must be directly used [e.g: (~a)]"
(syntax->datum stx))
stx)])))
(define-syntax (while stx)
(syntax-case stx ()
[(_)
(raise-syntax-error #f "missing test and body" stx)]
[(_ cond)
(raise-syntax-error #f "missing body" stx)]
[(_ cond body ...)
(syntax/loc stx
(let/ec fresh-break
(let loop ()
(when cond
(let/ec fresh-continue
(syntax-parameterize
([break (force-use-with-parens #'fresh-break)]
[continue (force-use-with-parens #'fresh-continue)])
(begin body ...)))
(loop)))))]))
;; By the way: it's a bit unclear what should happen if
;; someone tries using break and continue within the
;; context of a nested while loop's test... e.g.
;; (while true
;; (while (begin (break))
;; 'huh?)
;; 'what?)
;;
;; This particular implementation is implemented such that
;; the call to break will exit the outer loop. It is an odd
;; thing to think about, isn't it? :)
;;
;; It should be easy to syntactically restrict if this really
;; becomes an issue, by syntax-parameterizing error productions
;; in the context of evaluating the _cond_ition.
(define/contract (num-different-integers word)
(-> string? exact-integer?)
(define s (make-hash)) ;键不允许重复
(define n (string-length word))
(define p1 0)
(define p2 -1)
(while #t
(while( and (< p1 n) (not (char-numeric? (string-ref word p1))) )
(set! p1 (+ p1 1)))
; (displayln (format "save1 p1= ~a p2= ~a" p1 p2))
(when (>= p1 n) (break)) ;建议when. if cond都不好使
(set! p2 p1)
; (displayln (format "save2 p1= ~a p2= ~a" p1 p2))
(while( and (< p2 n) (char-numeric? (string-ref word p2)) )
(set! p2 (+ p2 1))
)
; (displayln (format "save3 p1= ~a p2= ~a" p1 p2))
(while( and (> (- p2 p1) 1) (string=? "0" (substring word p1 (+ p1 1))) )
(set! p1 (+ p1 1))
)
( hash-set! s (substring word p1 p2) 1 )
(set! p1 p2)
)
(displayln (format "s= ~a" s)) ;看看这个哈希表长啥样
(hash-count s)
)
;下面是草稿
; (while (<= p1 5)
; (set! p1 (+ p1 1))
; ; (displayln p1)
; (displayln (string=? "0" (substring word p1 (+ p1 1))) )
; )
