AtCoder ARC #053

arc053-a.rb

h, w = gets.chomp.split(" ").map(&:to_i)
puts (h - 1) * w + h * (w - 1)

arc053-b.rb

s = gets.chomp
d = Hash.new(0)
s.split("").each do |c|
  d[c] += 1
end
nodd = 0
chars = 0
d.each do |k, v|
  if v.odd?
    nodd += 1
  end
  chars += v / 2
end
if nodd == 0 then
  puts s.length
else
  puts chars / nodd * 2 + 1
end

arc053-c.rb

n = gets.chomp.to_i
dec = []
inc = []
while line = gets
  a, b = line.chomp.split(" ").map(&:to_i)
  if a < b then
    dec << [a, b]
  else
    inc << [a, b]
  end
end
dec.sort_by!{|v| v[0]}
inc.sort_by!{|v| -v[1]}
ans = 0
curr = 0
dec.each do |x|
  up, down = x
  ans = [ans, curr+up].max
  curr += (up - down)
end
inc.each do |x|
  up, down = x
  ans = [ans, curr+up].max
  curr += (up - down)  
end
puts ans