「瞬き星」を解いた

M=%w( AJIC CHGE EFJB BIHD DGFA ).map{ |x| "__"+x+"__"}

def try_filp( st, st0, line, ix, dir )
  me=st[line[ix]]
  if me==st0[line[ix+dir*2]]
    st[line[ix+dir]]=me
  elsif me==st0[line[ix+dir*3]]
    st[line[ix+dir]]=me
    st[line[ix+dir*2]]=me
  end
end

def process( st0, pos )
  st=st0.dup
  st[pos]^=1
  M.each do |line|
    ix=line.index(pos)
    next unless ix
    dir = [0,0,1,1,-1,-1][ix]
    try_filp( st, st0, line, ix, dir ) if st[pos] != st[line[ix+dir]]
  end
  st
end

def solve(src)
  st=[*?A..?E].each_with_object({}){|x,o|o[x]=1}
  [*?F..?J].each{|x| st[x]=0}
  src.each_char do |c|
    st=process(st, c)
  end
  [*?A..?J].map{ |x| st[x]==1 ? "W" : "R" }.join
end

DATA.map{ |line|
  src, expected = line.split(/\s+/)
  actual = solve( src )
  ok = actual==expected
  puts( "%s : %s->%s / %s" % [ (ok ? "ok" : "**NG**" ), src, actual, expected ] )
  ok
}.tap{ |x| puts( x.all? ? "all ok" : "something wrong" ) }

__END__
A RWWWWRRRRR
FGHIJABCDE  RRRRRRRRRR