add day 07: Bridge Repair

Author: petertseng

07_bridge_repair.rb

@@ -0,0 +1,22 @@
+verbose = ARGV.delete('-v')
+
+calib = ARGF.map { |line|
+  l, r = line.split(': ', 2)
+  [Integer(l), r.split.map(&method(:Integer)).freeze].freeze
+}.freeze
+
+# work from right to left
+
+tot = 0
+[false, true].each { |concat|
+  good, calib = calib.partition { |tv, vs|
+    make = ->(a, i) {
+      return vs[0] == a if i == 0
+      x = vs[i]
+      ((p10 = 10 ** x.to_s.size; make[a / p10, i - 1] if a % p10 == x) if concat) || (make[a / x, i - 1] if a % x == 0) || (make[a - x, i - 1] if x <= a)
+    }
+    make[tv, vs.size - 1]
+  }.map(&:freeze)
+  p good.map(&:first) if verbose
+  puts tot += good.sum(&:first)
+}

bench-rejected-impls/07_bridge_repair.rb

@@ -0,0 +1,86 @@
+require 'benchmark'
+
+bench_candidates = []
+
+bench_candidates << def drop1(calib)
+  calib.sum { |tv, vs|
+    vs.drop(1).reverse.reduce([tv]) { |acc, x|
+      acc.flat_map { |a|
+        [
+          (a - x if x <= a),
+          (a / x if a % x == 0),
+          (p10 = 10 ** x.to_s.size; a / p10 if a % p10 == x),
+        ].compact
+      }
+    }.include?(vs[0]) ? tv : 0
+  }
+end
+
+bench_candidates << def no_drop(calib)
+  calib.sum { |tv, vs|
+    vs.reverse.reduce([tv]) { |acc, x|
+      acc.flat_map { |a|
+        [
+          (a - x if x <= a),
+          # no_drop specifically needs a > 0, because it checks for 0 at the end!
+          (a / x if a > 0 && a % x == 0),
+          (p10 = 10 ** x.to_s.size; a / p10 if a % p10 == x),
+        ].compact
+      }
+    }.include?(0) ? tv : 0
+  }
+end
+
+bench_candidates << def rec_add_first(calib)
+  calib.sum { |tv, vs|
+    make = ->(a, i) {
+      return vs[0] == a if i == 0
+      x = vs[i]
+      (make[a - x, i - 1] if x <= a) || (make[a / x, i - 1] if a > 0 && a % x == 0) || (p10 = 10 ** x.to_s.size; make[a / p10, i - 1] if a % p10 == x)
+    }
+    make[tv, vs.size - 1] ? tv : 0
+  }
+end
+
+bench_candidates << def rec_mul_first(calib)
+  calib.sum { |tv, vs|
+    make = ->(a, i) {
+      return vs[0] == a if i == 0
+      x = vs[i]
+      (make[a / x, i - 1] if a > 0 && a % x == 0) || (make[a - x, i - 1] if x <= a) || (p10 = 10 ** x.to_s.size; make[a / p10, i - 1] if a % p10 == x)
+    }
+    make[tv, vs.size - 1] ? tv : 0
+  }
+end
+
+bench_candidates << def rec_concat_first(calib)
+  calib.sum { |tv, vs|
+    make = ->(a, i) {
+      return vs[0] == a if i == 0
+      x = vs[i]
+      (p10 = 10 ** x.to_s.size; make[a / p10, i - 1] if a % p10 == x) || (make[a / x, i - 1] if a > 0 && a % x == 0) || (make[a - x, i - 1] if x <= a)
+    }
+    make[tv, vs.size - 1] ? tv : 0
+  }
+end
+
+calib = ARGF.map { |line|
+  l, r = line.split(': ', 2)
+  [Integer(l), r.split.map(&method(:Integer)).freeze].freeze
+}.freeze
+
+# work from right to left
+
+results = {}
+
+Benchmark.bmbm { |bm|
+  bench_candidates.each { |f|
+    bm.report(f) { 100.times { results[f] = send(f, calib) } }
+  }
+}
+
+# Obviously the benchmark would be useless if they got different answers.
+if results.values.uniq.size != 1
+  results.each { |k, v| puts "#{k} #{v}" }
+  raise 'differing answers'
+end