AtCoder（AtCoder Beginners Selection）

PracticeA - はじめてのあっとこーだー（Welcome to AtCoder）

a = gets.to_i
b, c = gets.split.map(&:to_i)
s = gets
 
print "#{a + b + c} #{s}"

ABC086A - Product

a, b = gets.split.map(&:to_i)
puts (a * b).odd? ? "Odd" : "Even"

ABC081A - Placing Marbles

puts gets.chomp.count("1")

ABC081B - Shift only

def calc(ary, co)
  return co unless ary.all?(&:even?)
  calc(ary.map {|i| i / 2}, co + 1)
end

gets
given = gets.split.map(&:to_i)
puts calc(given, 0)

ABC087B - Coins

table = [500, 100, 50]
coins = 3.times.map {gets.to_i}
x = gets.to_i
memo = Array.new(4) {[]}

try = ->(i, yen) {
  return memo[i][yen] if memo[i][yen]
  return 1 if yen.zero?
  return 0 if i >= 3
  co = 0
  (0..coins[i]).each do |n|
    yen1 = yen - table[i] * n
    break if yen1 < 0
    co += try.(i + 1, yen1)
  end
  memo[i][yen] = co
}
puts try.(0, x)

ABC083B - Some Sums

n, a, b = gets.split.map(&:to_i)
puts (1..n).select {|i| i.to_s.bytes.map {|b| b - 48}.inject(&:+).between?(a, b)}
           .inject(&:+)

ABC088B - Card Game for Two

n = io.gets.to_i
cards = io.gets.split.map(&:to_i).sort
diff = 0

(0...n).each do |i|
  if i.even?
    diff += cards[n - 1 - i]
  else
    diff -= cards[n - 1 - i]
  end
end
puts diff

ABC085B - Kagami Mochi

n = gets.to_i
puts n.times.map {gets.to_i}.uniq.size

ABC085C - Otoshidama

n, y = gets.split.map(&:to_i)

limit1 = [y / 10000, n].min
(0..limit1).each do |b1|
  yen1 = y - 10000 * b1
  limit2 = [yen1 / 5000, n - b1].min
  (0..limit2).each do |b2|
    b3 = n - b1 - b2
    if yen1 == 5000 * b2 + 1000 * b3
      puts "#{b1} #{b2} #{b3}"
      exit
    end
  end
end
puts "-1 -1 -1"

これで 0.216秒。
よりよい方法がよく考えたらわかった。

n, y = gets.split.map(&:to_i)

limit1 = [y / 10000, n].min
(0..limit1).each do |b1|
  x = y / 1000 - n - 9 * b1
  if x >= 0 and (x % 4).zero?
    b2 = x / 4
    b3 = n - b1 - b2
    if b3 >= 0 and 10000 * b1 + 5000 * b2 + 1000 * b3 == y
      puts "#{b1} #{b2} #{b3}"
      exit
    end
  end
end
puts "-1 -1 -1"

これで 0.009秒。
　

ABC049C - 白昼夢 / Daydream

table = %w(dream dreamer erase eraser).map(&:reverse)
s = gets.chomp.reverse
result = "YES"

until s.length.zero?
  catch :jump do
    table.each do |word|
      n = word.length
      if s[0, n] == word
        s = s[n..-1]
        throw :jump
      end
    end
    result = "NO"
    s = ""
  end
end
puts result

ABC086C - Traveling

n = gets.to_i
plans = n.times.map {gets.split.map(&:to_i)}

f = plans.all? do |t, x, y|
  d = x.abs + y.abs
  if t < d
    false
  else
    t.odd? ? d.odd? : d.even?
  end
end
puts f ? "Yes" : "No"