AtCoder ARC #082 / ABC #072

arc082-a.rb

a, b = gets.chomp.split(" ").map(&:to_i)
puts [0, a - b].max

arc082-b.rb

s = gets.chomp.split("")
n = s.length
ret = []
n.times do |i|
  if (i + 1).odd?
    ret << s[i]
  end
end
puts ret.join("")

arc082-c.rb

n = gets.chomp.to_i
a = gets.chomp.split(" ").map(&:to_i)
b = Array.new(10**5+1, 0)
a.each do |i|
  b[i] += 1
end
ret = 0
b.each_cons(3) do |v1, v2, v3|
  ret = [ret, v1 + v2 + v3].max
end
puts ret

arc082-d.rb

n = gets.chomp.to_i
a = gets.chomp.split(" ").map(&:to_i)

ret = 0
curr = 1
i = 0
loop do
  break if i > n - 1
  if a[i] == curr
    ret += 1
    curr += 2
    i += 2
  else
    curr += 1
    i += 1
  end
end

puts ret