Submission #24393748

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Source Code Expand

N,M = gets.split.map(&:to_i)

E = Array.new(N){[]}
ヨ = Array.new(N){[]}
M.times{
	a,b = gets.split.map{_1.to_i-1}
	E[a] << b
	ヨ[b] << a
}

v,V = -1,[nil]*N
F = lambda{|a|
	V[a] = -1
	*q = a
	while a = q.pop
		0while b = E[a].pop and V[b]
		if b
			q << a << b
			V[b] = -1
		else
			V[a] = v+=1
		end
	end
}
N.times{|a|
	F[a] if ! V[a]
}

Q = [nil]*N
V.each_with_index{|i,a|
	Q[i] = a
}
V.fill nil
v = 0
while a = Q.pop
	next if V[a]
	V[a] = v+=1
	ヨ[a].each{|b|
		next if V[b]
		V[b] = v
	}
end

puts(v==N ? 'No':'Yes')

Submission Info

Judge Result