[2023][ruby][5.x]

2023/ruby/day_05.rb

@@ -0,0 +1,123 @@
+Conversion = Data.define(:source, :dest) do
+  def [](k)
+    return nil unless source.cover?(k)
+
+    dest.begin + k - source.begin
+  end
+end
+
+Mapping = Data.define(:conversions) do
+  def [](source)
+    conversions.filter_map { _1[source] }.first || source
+  end
+end
+
+chunks = ARGF.read.split("\n\n")
+seeds = chunks.shift.scan(/\d+/).map(&:to_i)
+mappings = chunks.map {|chunk|
+  Mapping.new(
+    chunk
+      .strip.split("\n")[1..-1]
+      .map { _1.scan(/\d+/).map(&:to_i) }
+      .map { Conversion.new((_2..._2+_3), (_1..._1+_3)) }
+      # .sort_by { _1.source.begin }
+  )
+}
+
+# part one
+p seeds
+  .map {|seed|
+    mappings.inject(seed) {|cur, mapping| mapping[cur] }
+  }
+  .min
+
+# part two
+
+# clamps range a to range b
+def clamp(a, b)
+  case
+  when a.cover?(b.begin) && a.cover?(b.end)
+    b
+  when b.cover?(a.begin) && b.cover?(a.end)
+    a
+  when a.cover?(b.begin)
+    (b.begin...a.end)
+  when b.cover?(a.begin)
+    (a.begin...b.end)
+  else
+    nil
+  end
+end
+
+seeds = seeds
+  .each_slice(2)
+  .map {|start, length| (start...start+length) }
+  .sort_by(&:begin)
+dests = mappings.inject(seeds) {|cur, mapping|
+  sources = cur
+    .flat_map {|range|
+      sources = mapping.conversions.map(&:source).sort_by(&:begin)
+      sources.concat(sources.each_cons(2).map { (_1.end..._2.begin) })
+      sources << (0...(sources.map(&:begin).min))
+      sources << (sources.map(&:end).max..)
+      sources.filter_map {|source|
+        clamp(source, range)
+      }
+    }
+    .reject { _1.size == 0 }
+  sources.map { (mapping[_1.begin]..mapping[_1.end-1]) }
+}
+p dests.map(&:begin).min
+
+### prior explorations for part two
+
+# p seeds
+#   .each_slice(2)
+#   .map {|start, length|
+#     (start...start+length).map {|seed|
+#       mappings.inject(seed) {|cur, mapping| mapping[cur] }
+#     }
+#     .min
+#   }
+#   .min
+
+# seeds = seeds
+#   .each_slice(2)
+#   .map {|start, length| (start...start+length) }
+# reversed = mappings
+#   .map {|mapping|
+#     Mapping.new(
+#       mapping.conversions.map {|c|
+#         Conversion.new((c.dest_start...c.dest_start+c.source_range.size), c.source_range.begin)
+#       }
+#     )
+#   }
+#   .reverse
+# p (0..).find {|i|
+#     source = reversed.inject(i) {|cur, mapping| mapping[cur] }
+#     seeds.any? { _1.cover?(source) }
+#   }
+
+# seeds = seeds
+#   .each_slice(2)
+#   .map {|start, length| (start...start+length) }
+reversed = mappings
+  .map {|mapping|
+    Mapping.new(
+      mapping.conversions.map {|c|
+        Conversion.new((c.dest.begin...c.dest.begin+c.source.size), c.source)
+      }
+    )
+  }
+  .reverse
+lowest = seeds
+  .flat_map(&:minmax)
+  .filter_map {|seed|
+    mappings.inject(seed) {|cur, mapping| mapping[cur] }
+  }
+  .min
+p (0..lowest).bsearch {|loc|
+    source = reversed.inject(loc) {|cur, mapping| mapping[cur] }
+    seeds.any? { _1.cover?(source) }
+  }
+