東京大学 情報理工学系研究科 創造情報学専攻 2021年8月実施 プログラミング 第1問

Author

itsuitsuki

Description (English)

Answer the following questions by writing programs. If you are taking an onsite examination, the files needed for answering the questions are found in the USB flash drive. Store the programs in the USB flash drive before the examination ends. Also the files generated for answering questions must be stored in the USB flash drive. If you are taking an online replacement examination, the files needed for answering the questions are in the given zip file. To submit the programs and the files, follow the instructions separately given. The submission URL is shown on the last page.

We store the daily numbers of newly infected people with some virus (new infections, below) in a text file in chronological order. The numbers are separated by colons (:). For example, when the numbers of new infections for 5 days are

621 591 907 1121 1032

the following text

621:591:907:1121:1032

is stored in a file.

Problem

(1) Find the 10th biggest number of new infections stored in the text file infections.txt and write it on the answer sheet. Count after removing duplicate numbers. For example, the third biggest number among 1, 2, 3, 3, 4 is 2.

(2) For every text file in the data folder, find , the 10th biggest number of new infections in , as in Question (1). Then calculate the sum of all and write it on the answer sheet.

(3) For , the numbers of new infections stored in the text file infections.txt, the new-infection increment on a day is the difference between the number of the new infections on that day and on the day before. Here, the number of new infections on the day before the first day is zero.

Concatenate the new-infection increment for every day into one character sequence and store it in the text file diff.txt. Furthermore, count the characters in this sequence and write that number on the answer sheet. The newline character is not counted. Start with + for a non-negative number and start with - for a negative number.

For example, when the new-infection increments are

621 -30 0 -316 214 -89

the following character sequence

+621-30+0-316+214-89

is stored and the number of characters is 20.

(4) For the numbers of new infections in the text file infections.txt, find the shortest period among the periods in which the sum of the new-infection increments is maximized. Write that period on the answer sheet. If more than one such period is found, write all the periods. The first day is Day 1. For example, answer like "From Day 8 to 24". Furthermore, calculate the sum of the new-infection increments during that period, and write that sum on the answer sheet.

Kai