问题

定义一个20*5的二维数组，用来存储某班级20位学员的5门课的成绩；这5门课按存储顺序依次为：core C++，coreJava，Servlet，JSP和EJB。 （1）循环给二维数组的每一个元素赋0~100之间的随机整数。 （2）按照列表的方式输出这些学员的每门课程的成绩。 （3）要求编写程序求每个学员的总分，将其保留在另外一个一维数组中。 （4）要求编写程序求所有学员的某门课程的平均分。

解决（python）

  1.   1. #! /usr/bin/env python
  2.     2. #coding:utf-8
  3.     3.   4. from __future__ import division
  4.     5. import random
  5.     6.   7.   8. def score(score_list,course_list,student_num):
  6.     9.     course_num = len(course_list)
  7.     10.   11.     every_score = [[score_list[j][i] for j in range(course_num)] for i in range(student_num)]
  8.     12.   13.     every_total = [sum(every_score[i]) for i in range(student_num)]
  9.     14.   15.     ave_course = [sum(score_list[i])/len(score_list[i]) for i in range(len(score_list))]
  10.     16.   17.     return (every_score,every_total,ave_course)
  11.     18.   19. if __name__=="__main__":
  12.     20.   21.     course_list = ["C++","Java","Servlet","JSP","EJB"]
  13.     22.     student_num = 20
  14.     23.   24.     score_list = [[random.randint(0,100) for i in range(student_num)] for j in range(len(course_list))]
  15.     25.     for i in range(len(course_list)):
  16.     26.         print "score of every one in %s:"%course_list[i]
  17.     27.         print score_list[i]
  18.     28.   29.     every_score,every_total,ave_one_course = score(score_list,course_list,student_num)
  19.     30.     print "\n"
  20.     31.     print "NEXT IS EVERY ONE SCORE IN EVERY COURSE:"
  21.     32.     for name in course_list:
  22.     33.         print name,
  23.     34.     print "\t"
  24.     35.     print every_score
  25.     36.     print "\n"
  26.     37.     print "every one all score:\t",every_total
  27.     38.     print "every course of average score:\t",ave_one_course

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解法 (racket 5.2.1)

  1.   1. #lang racket
  2.     2.   3. (define (2d-list)
  3.     4.   (let*
  4.     5.     ([rand-100 (lambda () (random 101))]
  5.     6.      [nth-picker (lambda (n) (lambda (l) (list-ref l n)))]
  6.     7.      [average (lambda (number-list) (exact->inexact (/ (apply + number-list) (length number-list))))]
  7.     8.      [course-list (list "coreC++" "coreJava" "Servlet" "JSP" "EJB")]
  8.     9.      [score-list (for/list ([i 20]) (for/list ([j 5]) (rand-100)))]
  9.     10.      [score-by-course-list (for/list ([i 5]) (list ((nth-picker i) course-list) (map (nth-picker i) score-list)))]
  10.     11.      [score-by-student-list (for/list ([i 20]) (list-ref score-list i))]
  11.     12.      [total-by-student-list (for/list ([i 20]) (apply + (list-ref score-list i)))]
  12.     13.      [average-by-course-list (for/list ([i 5]) (list ((nth-picker i) course-list) (average (map (nth-picker i) score-list))))])
  13.     14.     (for ([i 5]) 
  14.     15.       (display "score of every one in ")
  15.     16.       (displayln (first ((nth-picker i) score-by-course-list)))
  16.     17.       (displayln (second ((nth-picker i) score-by-course-list))))
  17.     18.     (displayln "")
  18.     19.     (displayln "NEXT IS EVERY ONE SCORE IN EVERY COURSE: ")
  19.     20.     (displayln course-list)
  20.     21.     (for ([i 10]) 
  21.     22.       (displayln (list-ref score-by-student-list i)))
  22.     23.     (displayln "")
  23.     24.     (displayln "every one all score: ")
  24.     25.     (displayln total-by-student-list)
  25.     26.     (displayln "")
  26.     27.     (displayln "every course of average score: ")
  27.     28.     (displayln average-by-course-list)))
  28.     29.   30. ; 调用函数, 正常时应输出类似如下结果
  29.     31. ;score of every one in coreC++
  30.     32. ;(12 58 60 28 78 23 34 83 19 83 78 26 51 94 93 74 53 89 8 23)
  31.     33. ;... ...
  32.     34. ;NEXT IS EVERY ONE SCORE IN EVERY COURSE: 
  33.     35. ;(coreC++ coreJava Servlet JSP EJB)
  34.     36. ;(12 49 75 88 68)
  35.     37. ;(58 78 6 88 81)
  36.     38. ;... ...
  37.     39. ;every one all score: 
  38.     40. ;(292 311 370 241 289 250 254 258 147 232 271 170 224 248 317 286 246 270 186 212)
  39.     41. ;
  40.     42. ;every course of average score: 
  41.     43. ;((coreC++ 53.35) (coreJava 53.9) (Servlet 51.95) (JSP 49.6) (EJB 44.9))
  42.     44. (2d-list)

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