[教學] Programming 13: "Peano Jordan"

題目網址

時間限制：4秒

題目大意：

給定一函數p(x)、區間[x1,x2]，求出以"中位數"為基、每0.01單位分割的面積積分。



解法：

利用 Ruby eval函數的特性，做好字串處理後直接交給它處理。
要注意的是必須加入.to_f讓 Ruby 知道是用float進行運算。

以下程式以 Ruby 執行：

# Author      : mashimaro
# Last Modify : 2008/01/02

require 'digest/md5'
require 'net/http'
require 'net/https'

host = 'www.bright-shadows.net'
path = '/challenges/programming/peanojordan/tryout.php'
cookie = 'PHPSESSID=**********************************'

http = Net::HTTP.new(host, 80)
#http.use_ssl = true
headers = {
  'Cookie' => cookie,
#  'Referer' => 'http://profil.wp.pl/login.html',
#  'Content-Type' => 'application/x-www-form-urlencoded'
}

while(true)

 resp, data = http.get(path, headers);

 data.sub!('<pre>', '');
 data.sub!('</pre>', '');

 lines = data.split('<br>');

 exp = lines[0].sub('p(x) = ', '').gsub('/','.to_f/').gsub('^','**');
 a, b = lines[2].scan(/[\-0-9]+/);

 int_1 = a.to_i;
 int_2 = b.to_i;

 puts '';
 puts lines[0];
 puts '';
 puts lines[2];
 puts '';
 puts exp;
 #puts int_1, int_2;
 puts '';

 break if(exp[-1..-1].to_i < 6);

end

sum = 0;
int_1 = int_1 + 0.005;

while(int_1 < int_2)

 sum = sum + eval(exp.gsub('x','('+int_1.to_s+')'));
 puts sum;

 int_1 = int_1 + 0.01;

end

puts (sum * 0.01).round;

digest = Digest::MD5.hexdigest((sum * 0.01).round.to_s);
ret_path = '/challenges/programming/peanojordan/solution.php?solution=' + digest;

resp, data = http.get(ret_path, headers);

puts data;

消息來源