问题

解决（python）

解法 (racket 5.2.1)

  3. (define (2d-list)
  4.   (let*
  5.     ([rand-100 (lambda () (random 101))]
  6.      [nth-picker (lambda (n) (lambda (l) (list-ref l n)))]
  7.      [average (lambda (number-list) (exact->inexact (/ (apply + number-list) (length number-list))))]
  8.      [course-list (list "coreC++" "coreJava" "Servlet" "JSP" "EJB")]
  9.      [score-list (for/list ([i 20]) (for/list ([j 5]) (rand-100)))]
  10.      [score-by-course-list (for/list ([i 5]) (list ((nth-picker i) course-list) (map (nth-picker i) score-list)))]
  11.      [score-by-student-list (for/list ([i 20]) (list-ref score-list i))]
  12.      [total-by-student-list (for/list ([i 20]) (apply + (list-ref score-list i)))]
  13.     (for ([i 5]) 
  15.       (displayln (first ((nth-picker i) score-by-course-list)))
  16.       (displayln (second ((nth-picker i) score-by-course-list))))
  17.     (displayln "")
  18.     (displayln "NEXT IS EVERY ONE SCORE IN EVERY COURSE: ")
  19.     (displayln course-list)
  20.     (for ([i 10]) 
  21.       (displayln (list-ref score-by-student-list i)))
  22.     (displayln "")
  23.     (displayln "every one all score: ")
  24.     (displayln total-by-student-list)
  25.     (displayln "")
  26.     (displayln "every course of average score: ")
  27.     (displayln average-by-course-list)))
  28. ; 调用函数, 正常时应输出类似如下结果
  29. ;score of every one in coreC++
  30. ;(12 58 60 28 78 23 34 83 19 83 78 26 51 94 93 74 53 89 8 23)
  31. ;... ...
  32. ;NEXT IS EVERY ONE SCORE IN EVERY COURSE: 
  33. ;(coreC++ coreJava Servlet JSP EJB)
  34. ;(12 49 75 88 68)
  35. ;(58 78 6 88 81)
  36. ;... ...
  37. ;every one all score: 
  38. ;(292 311 370 241 289 250 254 258 147 232 271 170 224 248 317 286 246 270 186 212)
  39. ;
  40. ;every course of average score: 
  42. (2d-list)