AtCoder ABC #067 / ARC #078

arc078-a.rb

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

if a % 3 == 0 || b % 3 == 0 || (a + b) % 3 == 0 then
  puts "Possible"
else
  puts "Impossible"
end

arc078-b.rb

n, k = gets.chomp.split(" ").map(&:to_i)
l = gets.chomp.split(" ").map(&:to_i).sort.reverse

puts l[0...k].inject(:+)

arc078-c.rb

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

b = [a[0]]
(1..(n - 1)).each do |i|
  b << b[i-1] + a[i]
end

a_sum = b[n-1]
ans = (b.shift * 2 - a_sum).abs
b.pop
b.each do |x|
  ans = [ans, (2 * x - a_sum).abs].min
end

puts ans

arc078-d.rb

@n = gets.chomp.to_i

@nodes = Array.new(@n+1){Array.new()}

(@n - 1).times do
  a, b = gets.chomp.split(" ").map(&:to_i)
  @nodes[a] << b
  @nodes[b] << a
end

def dfs(start)
  que = [start]
  visited = Array.new(@n+1, false)
  dist = Array.new(@n+1, 0)
  while !que.empty?
    node = que.shift
    visited[node] = true
    @nodes[node].each do |i|
      if visited[i] then
        next
      else
        que << i
        dist[i] = dist[node] + 1
      end
    end
  end
  return dist
end

dist1 = dfs(1)
dist2 = dfs(@n)

fennec = 0
snuke = 0
(1..@n).each do |i|
  if dist1[i] <= dist2[i] then
    fennec += 1
  else
    snuke += 1
  end
end

if fennec > snuke then
  puts "Fennec"
else
  puts "Snuke"
end