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

qiwsir#gmail.com (# to @)

解法 (racket 5.2.1)

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