Submission #794169

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Source Code Expand

n, m = gets.chomp.split(' ').map(&:to_i)
x = []
y = []
h = Hash.new { |hsh, key| hsh[key] = [] }
m.times do |i|
  x[i], y[i] = gets.chomp.split(' ').map(&:to_i)
  h[y[i]] << x[i]
end
curarr = Array.new(n)
def count(arr, idx, hsh, n)
  ans = 0
  return 1 if idx == n
  n.times do |i|
    bool = false
    arr.each do |j|
      hsh[j].each do |k|
        bool = true if k == i + 1
      end
    end
    next if arr.include?(i + 1) || bool
    nextarr = Array.new(arr)
    nextarr[idx] = i + 1
    # puts "curarr = #{nextarr}, curidx = #{idx}"
    ans += count(nextarr, idx + 1, hsh, n)
  end
  ans
end
puts count(curarr, 0, h, n)

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