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cia_rana 今週のお題：グループで乗るリフト

Updated by cia_rana
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File codeiq.3177.rb Modified

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 def combination(n, k)
   k = n - k if k * 2 > n
-  return 1 if k == 0
-  ((n - k + 1)..n).reduce(:*)/(1..k).reduce(:*)
+  k == 0 ? 1 : ((n - k + 1)..n).reduce(:*)/(1..k).reduce(:*)
 end
 
 def calc_pattern(m, n, max_num)
Updated by cia_rana
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File codeiq.3177.rb Modified

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 end
 
 m, n = gets.split.map(&:to_i)
-puts ((1.0*m/n).ceil..m).inject(0){|sum, r|
+p ((1.0*m/n).ceil..m).inject(0){|sum, r|
   sum + calc_pattern(r, m, n)
 }
Created by cia_rana
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File codeiq.3177.rb Added

  • Ignore whitespace
  • Hide word diff 
+def combination(n, k)
+  k = n - k if k * 2 > n
+  return 1 if k == 0
+  ((n - k + 1)..n).reduce(:*)/(1..k).reduce(:*)
+end
+
+def calc_pattern(m, n, max_num)
+  (0..(k = n - m)/max_num).reduce(0) { |s, i| s + [1, -1][i % 2] * combination(m, i) * combination(m + k - 1 - max_num * i, m - 1) }
+end
+
+m, n = gets.split.map(&:to_i)
+puts ((1.0*m/n).ceil..m).inject(0){|sum, r|
+  sum + calc_pattern(r, m, n)
+}
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