Codeforces #410 Div2

cf410-a.rb

s = gets.chomp
n = s.length
ret = 0
if n == 1 then
  puts "YES"
  exit
elsif n.odd? then
  ((n - 1) / 2).times do |i|
    if s[i] != s[n - 1 - i] then
      ret += 1
    end
  end  
  if ret <= 1 then
    puts "YES"
  else
    puts "NO"
  end
else
  (n / 2).times do |i|
    if s[i] != s[n - 1 - i] then
      ret += 1
    end
  end
  if ret == 1 then
    puts "YES"
  else
    puts "NO"
  end
end

cf410-b.rb

# WA
n = gets.chomp.to_i
a = []
h = Hash.new{|hash, key| hash[key] = Array.new()}
n.times do
  s = gets.chomp
  a << s
end
nn = a[0].length
a.each do |s|
  nn.times do |i|
    ss = s[i...nn] + s[0...i]
    h[ss] << i
  end
end
if h.size != nn then
  puts -1
else
  puts h.values.map{|v| v.inject(:+)}.min
end