ojs = {}
ojs["poj"] = :A
ojs["hdu"] = :A
ojs["uva"] = :B
ojs["zoj"] = :B
ojs["CF"] = :S
ojs["TC"] = :S
ratings = Hash.new(0)
ojs.values.each { |rate| ratings[rate] += 1 }
 print ratings
 puts ""
 puts "==============================="
 print ojs
 puts ""
 puts "==============================="
 3.times {print "hey!"}
 puts ""
 puts "==============================="
 
 print ojs.length
 puts ""
 print ojs.keys
 puts ""
 print ojs.values
 puts ""
 ojs.keys.each { |name| print name; print " "; print ojs[name]; puts ""; }
 puts "==============================="
 print File.read("x.txt")
 puts "==============================="
 File.open("x.txt", "a") do |f|
   f << "HACKED!\n"
   end
 print File.read("x.txt")
 puts "==============================="
 print File.mtime("x.txt")
 puts ""
 print File.mtime("x.txt").hour
 puts ""
 puts "==============================="

# 读取一个文件的数据库并且输出
def load_oj( path )
 ojs = {}
  File.foreach(path) do |line|
  name, value = line.split(':')
  ojs[name] = value
 end
 print_oj(ojs)
end
def print_oj( data )
 puts "================================"
 print "name\tvalue\n"
 data.keys.each do |name|
  puts "#{name}\t#{data[name]}"
 end
 puts "================================"
end
oj = load_oj("x.txt")

# 从文件中读取学生信息并且输出
class Student
#attr_accessor :name
#attr_accessor :number
def initialize(name = "Unknown", number = "2012309999")
@name = name
@number = number
end
def print
puts "#{@name}\t#{@number}"
end
end
def load_stu( path )
data = {}
File.foreach(path) do |line|
na, no = line.split(' ')
s = Student.new(no, na)
data[s] = 1
end
data
end
def print_stu( data )
puts "================================"
print "name\tnumber\n"
data.keys.each do |stu|
stu.print
end
puts "================================"
end
data = load_stu("y.txt")
print_stu(data)

# 一行内输入4个整数，计算这四个数的最大公约数
def gcd(a, b)
 if b === 0
  return a
 else return gcd(b, a % b)
 end
end
str = gets.chomp
a, b, c, d = str.split(" ")
g1 = gcd(a.to_i, b.to_i);
g2 = gcd(c.to_i, d.to_i);
g3 = gcd(g1, g2)
puts "gcd(#{a}, #{b}, #{c}, #{d}) = #{g3}"