gistfile1.vim

function! s:hoge(xs)
  let top = get(a:xs,0,[])
  let rest = a:xs[1:]
  let i = 0
  while i < len(rest)
    for e in top
      if -1 < index(get(rest,i,[]), e)
        let top = uniq(sort(top + rest[i]))
        call remove(rest,i)
        let i = -1
        break
      endif
    endfor
    let i += 1
  endwhile
  if 1 < len(rest)
    return [top] + s:hoge(rest)
  else
    return [top] + rest
  endif
endfunction
echo s:hoge([[1,3],[3,4],[3,5],[5,6],[3,8],[9],[0],[4,11]])