Submission #26353383

Source Code Expand

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N = gets.to_i
P = 998244353
E = Array.new(N+1){[]}
$<.each{|ln|
  u,v = ln.split.map(&:to_i)
  E[u]<<v
  E[v]<<u
}
Ds = lambda{|s,p=s|
  vs = []
  vs << [s]
  ds = [-1]+[nil]*N
  ds[p],ds[s] = -1,0
  *q = s
  while u = q.pop
    d = ds[u]+1
    vd = vs[d]||=[]
    E[u].each{|v|
      next if ds[v]
      ds[v] = d
 
 
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N = gets.to_i
P = 998244353
E = Array.new(N+1){[]}
$<.each{|ln|
	u,v = ln.split.map(&:to_i)
	E[u]<<v
	E[v]<<u
}

Ds = lambda{|s,p=s|
	vs = []
	vs << [s]
	ds = [-1]+[nil]*N
	ds[p],ds[s] = -1,0
	*q = s
	while u = q.pop
		d = ds[u]+1
		vd = vs[d]||=[]
		E[u].each{|v|
			next if ds[v]
			ds[v] = d
			vd << v
			q << v
		}
	end
	vs.pop if vs[-1].empty?
	next vs
}
Ds1 = Ds[1]
Vd1 = Ds1[-1][0]
DsVd1 = Ds[Vd1]
Vd2 = DsVd1[-1][0]
DsVd2 = Ds[Vd2]
D = DsVd1.size-1

if D&1<1
	Vc, = DsVd1[D/2]&DsVd2[D/2]
	Eds = E[Vc].map{|v| (Ds[v,Vc][D/2-1]||[]).size }
	p (Eds.inject(1){|a,n| a*(n+1)%P }-1-Eds.sum)%P
else
	Vc1, = DsVd1[D/2]&DsVd2[D/2+1]
	Vc2, = DsVd2[D/2]&DsVd1[D/2+1]
	p Ds[Vc1,Vc2][-1].size*Ds[Vc2,Vc1][-1].size%P
end

Submission Info

Judge Result