AtCoder ABC #045

abc045-a.rb

# AC
a = gets.chomp.to_i
b = gets.chomp.to_i
h = gets.chomp.to_i
puts (a + b) * h / 2

abc045-b.rb

# AC
a = gets.chomp.split("")
b = gets.chomp.split("")
c = gets.chomp.split("")
  
nex = a.shift
while true
  if nex == "a" then
    nxar = a
    if nxar.empty? then
      puts "A"
      exit
    end
  elsif nex == "b" then
    nxar = b
    if nxar.empty? then
      puts "B"
      exit
    end
  elsif nex == "c" then
    nxar = c
    if nxar.empty? then
      puts "C"
      exit
    end
  end
  nex = nxar.shift
end

abc045-c-2.rb

# AC
s = gets.chomp.split("").map(&:to_i)
n = s.size
 
def base10(arr)
  n = arr.size - 1
  return n.downto(0).map{|x| arr[n - x]*10**x}.inject(:+)
end
 
if n == 1 then
  puts s[0]
else
  ans = [base10(s)]
  idxar = (1..(n-1)).to_a
  (1..(n-1)).each do |i|
    idxar.combination(i).each do |x|
      x = [0] + x + [n]
      ans << x.each_cons(2).map{|from, to| s.slice(from, (to - from))}.map{|arr| base10(arr)}.inject(:+)
    end
  end
  puts ans.inject(:+)
end

abc045-c.rb

# AC
s = gets.chomp
n = s.length

ans = 0
(1 << (n - 1)).times do |mask|
  expr = []
  (0...n).each do |i|
    if (mask & (1 << i)).zero? then
      expr += [s[i]]
    else
      expr += [s[i], "+"]
    end
  end
  ans += eval(expr.join)
end
puts ans