AtCoder DDCP 2016 予選 [Ruby]

ddcp2016-qual-a.rb

a, b, c = gets.chomp.split(" ").map(&:to_f)
puts c / a * b

ddcp2016-qual-b.rb

r, n, m = gets.chomp.split(" ").map(&:to_i)
w = 2 * r.to_f / n
aa = [0]
(1..(n - 1)).each do |i|
  a = w * i < r ? r - w * i : w * i - r
  aa << Math.sqrt(r ** 2 - a ** 2) * 2
end
aa << 0
ret = 0
(1..(n + m - 1)).each do |i|
  if i < 0 || i > n then
    ret += aa[i - m]
  elsif  i - m < 0 || i - m > n then
    ret += aa[i]
  else
    ret += [aa[i], aa[i - m]].max
  end
end
  
puts ret

ddcp2016-qual-c.rb

n, k = gets.chomp.split(" ").map(&:to_i)
aa = gets.chomp.split(" ").map(&:to_i)
h = Hash.new(0)
aa.each do |x|
  a = x.gcd(k)
  h[a] += 1
end
ret = 0
h.keys.repeated_combination(2).each do |a, b|
  next if (a * b) % k != 0
  if a == b then
    ret += h[a] * (h[b] - 1) / 2
  else
    ret += h[a] * h[b]
  end
end
puts ret