# 问题

（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）

``````#! /usr/bin/env python
#coding:utf-8

from __future__ import division
import random

def score(score_list,course_list,student_num):
course_num = len(course_list)

every_score = [[score_list[j][i] for j in range(course_num)] for i in range(student_num)]

every_total = [sum(every_score[i]) for i in range(student_num)]

ave_course = [sum(score_list[i])/len(score_list[i]) for i in range(len(score_list))]

return (every_score,every_total,ave_course)

if __name__=="__main__":

course_list = ["C++","Java","Servlet","JSP","EJB"]
student_num = 20

score_list = [[random.randint(0,100) for i in range(student_num)] for j in range(len(course_list))]
for i in range(len(course_list)):
print "score of every one in %s:"%course_list[i]
print score_list[i]

every_score,every_total,ave_one_course = score(score_list,course_list,student_num)
print "\n"
print "NEXT IS EVERY ONE SCORE IN EVERY COURSE:"
for name in course_list:
print name,
print "\t"
print every_score
print "\n"
print "every one all score:\t",every_total
print "every course of average score:\t",ave_one_course
``````

# 解法 (racket 5.2.1)

``````#lang racket

(define (2d-list)
(let*
([rand-100 (lambda () (random 101))]
[nth-picker (lambda (n) (lambda (l) (list-ref l n)))]
[average (lambda (number-list) (exact->inexact (/ (apply + number-list) (length number-list))))]
[course-list (list "coreC++" "coreJava" "Servlet" "JSP" "EJB")]
[score-list (for/list ([i 20]) (for/list ([j 5]) (rand-100)))]
[score-by-course-list (for/list ([i 5]) (list ((nth-picker i) course-list) (map (nth-picker i) score-list)))]
[score-by-student-list (for/list ([i 20]) (list-ref score-list i))]
[total-by-student-list (for/list ([i 20]) (apply + (list-ref score-list i)))]
[average-by-course-list (for/list ([i 5]) (list ((nth-picker i) course-list) (average (map (nth-picker i) score-list))))])
(for ([i 5])
(display "score of every one in ")
(displayln (first ((nth-picker i) score-by-course-list)))
(displayln (second ((nth-picker i) score-by-course-list))))
(displayln "")
(displayln "NEXT IS EVERY ONE SCORE IN EVERY COURSE: ")
(displayln course-list)
(for ([i 10])
(displayln (list-ref score-by-student-list i)))
(displayln "")
(displayln "every one all score: ")
(displayln total-by-student-list)
(displayln "")
(displayln "every course of average score: ")
(displayln average-by-course-list)))

; 调用函数, 正常时应输出类似如下结果
;score of every one in coreC++
;(12 58 60 28 78 23 34 83 19 83 78 26 51 94 93 74 53 89 8 23)
;... ...
;NEXT IS EVERY ONE SCORE IN EVERY COURSE:
;(coreC++ coreJava Servlet JSP EJB)
;(12 49 75 88 68)
;(58 78 6 88 81)
;... ...
;every one all score:
;(292 311 370 241 289 250 254 258 147 232 271 170 224 248 317 286 246 270 186 212)
;
;every course of average score:
;((coreC++ 53.35) (coreJava 53.9) (Servlet 51.95) (JSP 49.6) (EJB 44.9))
(2d-list)
``````