diff --git a/src/advent/day1.rb b/src/advent/day1.rb
index a911594..57d6ed5 100644
--- a/src/advent/day1.rb
+++ b/src/advent/day1.rb
@@ -39,7 +39,7 @@ def get_calibration_code(line)
 end
 
 def get_sum_of_calibration_code(document)
-  calibration_codes = document.split("\n").hash do |line|
+  calibration_codes = document.split("\n").map do |line|
     get_calibration_code line
   end
   calibration_codes.reduce 0, :+
diff --git a/src/advent/day2.rb b/src/advent/day2.rb
index 4da225f..cd3e6da 100644
--- a/src/advent/day2.rb
+++ b/src/advent/day2.rb
@@ -43,13 +43,13 @@ class Game
   def self.deserialize(line)
     id = /\s*Game\s+(\d+):/.match(line)[1].to_i
     draws_as_text = line[line.index(":") + 1..]
-    draws = draws_as_text.split(";").hash(&Draw.method(:deserialize))
+    draws = draws_as_text.split(";").map(&Draw.method(:deserialize))
     self.new id, draws
   end
 
   def fewer_number_of_cubes
     [:blue, :red, :green].map do |color|
-      @draws.hash {|draw| draw.send color }
+      @draws.map {|draw| draw.send color }
             .max || 0
     end
   end
diff --git a/src/advent/day3.rb b/src/advent/day3.rb
index 261fc92..840be26 100644
--- a/src/advent/day3.rb
+++ b/src/advent/day3.rb
@@ -98,7 +98,7 @@ class EngineLine
 
   def extract_engine_numbers
     digit_indexes = extract_digit_indexes @line
-    group_digit_indexes(digit_indexes).hash &method(:create_engine_number)
+    group_digit_indexes(digit_indexes).map &method(:create_engine_number)
   end
 
   def extract_gears
@@ -119,13 +119,13 @@ class Engine
   end
 
   def self.deserialize(ser)
-    els = ser.strip.split("\n").each_with_index.hash { |line, idx| EngineLine.new idx, line}
+    els = ser.strip.split("\n").each_with_index.map { |line, idx| EngineLine.new idx, line}
     return self.new els
   end
 
   def extract_engine_numbers
     @engine_lines
-      .hash {|line| line.extract_engine_numbers}
+      .map {|line| line.extract_engine_numbers}
       .flatten
   end
 
@@ -159,7 +159,7 @@ class Engine
 
   def is_adjacent(engine_number, gear)
     gear.get_neighbourhood
-        .hash {|point| engine_number.is_located_on(point[:line_index], point[:column_index])}
+        .map {|point| engine_number.is_located_on(point[:line_index], point[:column_index])}
         .any?
   end
 
@@ -170,15 +170,15 @@ class Engine
 
   def extract_gears
     @engine_lines
-      .hash {|line| line.extract_gears}
+      .map {|line| line.extract_gears}
       .flatten
   end
 
   def get_gear_ratios
     extract_gears
-      .hash {|gear| get_adjacent_number_parts(gear)}
+      .map {|gear| get_adjacent_number_parts(gear)}
       .filter {|adjacent_numbers| adjacent_numbers.length == 2}
-      .hash {|adjacent_numbers| adjacent_numbers.hash {|a| a.value}.reduce(1, :*)}
+      .map {|adjacent_numbers| adjacent_numbers.map {|a| a.value}.reduce(1, :*)}
   end
   attr_accessor :engine_lines
 end
@@ -190,6 +190,6 @@ input_content = File.open(input_file_name).read
 
 engine = Engine.deserialize input_content
 
-puts engine.extract_engine_numbers_that_touches_symbols.hash {|e| e.value}.sum
+puts engine.extract_engine_numbers_that_touches_symbols.map {|e| e.value}.sum
 puts engine.get_gear_ratios.sum
 
diff --git a/src/advent/day3_test.rb b/src/advent/day3_test.rb
index dd2fb00..c55015d 100644
--- a/src/advent/day3_test.rb
+++ b/src/advent/day3_test.rb
@@ -36,6 +36,7 @@ class Day3Test < Test::Unit::TestCase
     assert_equal [1, 2] + [3, 4], [1,2,3,4]
 
 
+    # assert_equal ((1..5) + (6..10)).to_a,  [1,2,3,4,5,6,7,8,9,10]
 
   end
 end
@@ -67,7 +68,7 @@ class EngineLineTest < Test::Unit::TestCase
   def test_extract_engine_numbers
     engine = Engine.deserialize @@easy_engine
     expt = [467, 114, 35, 633, 617, 58, 592, 755, 664, 598]
-    assert_equal expt, engine.extract_engine_numbers.hash {|e| e.value}
+    assert_equal expt, engine.extract_engine_numbers.map {|e| e.value}
   end
 
   def test_touches_symbol
@@ -79,7 +80,7 @@ class EngineLineTest < Test::Unit::TestCase
   def test_extract_engine_numbers_that_touches_symbols
     engine = Engine.deserialize @@easy_engine
     expt = [467, 35, 633, 617, 592, 755, 664, 598]
-    assert_equal expt, engine.extract_engine_numbers_that_touches_symbols.hash {|e| e.value}
+    assert_equal expt, engine.extract_engine_numbers_that_touches_symbols.map {|e| e.value}
   end
 
   def test_empty
@@ -96,14 +97,14 @@ class EngineLineTest < Test::Unit::TestCase
 .........."
     engine = Engine.deserialize input
     expt = []
-    assert_equal expt, engine.extract_engine_numbers_that_touches_symbols.hash {|e| e.value}
+    assert_equal expt, engine.extract_engine_numbers_that_touches_symbols.map {|e| e.value}
   end
 
 
   def test_day_3_part_1_easy
     engine = Engine.deserialize @@easy_engine
     expt = 4361
-    assert_equal expt, engine.extract_engine_numbers_that_touches_symbols.hash {|e| e.value}.sum
+    assert_equal expt, engine.extract_engine_numbers_that_touches_symbols.map {|e| e.value}.sum
   end
 
   def test_extract_gears
diff --git a/src/advent/day4.rb b/src/advent/day4.rb
index 0a3a33e..bfb80d3 100644
--- a/src/advent/day4.rb
+++ b/src/advent/day4.rb
@@ -19,8 +19,8 @@ class Card
   def self.deserialize(line)
     id_match = /Card\s+(\d+)/.match(line)
     id = id_match[1].to_i
-    winning_numbers = line[(line.index(":") + 1)..(line.index("|") - 1)].split(/\s+/).filter {|x| !x.empty?}.hash {|x| x.to_i}
-    selected_numbers = line[(line.index("|") + 1)..line.length].split(/\s+/).filter {|x| !x.empty?}.hash {|x| x.to_i}
+    winning_numbers = line[(line.index(":") + 1)..(line.index("|") - 1)].split(/\s+/).filter {|x| !x.empty?}.map {|x| x.to_i}
+    selected_numbers = line[(line.index("|") + 1)..line.length].split(/\s+/).filter {|x| !x.empty?}.map {|x| x.to_i}
     Card.new id, selected_numbers, winning_numbers
   end
 
@@ -40,12 +40,12 @@ class Cards
     cards = ser
               .split("\n")
               .filter {|line| !line.empty?}
-              .hash {|line| Card.deserialize line}
+              .map {|line| Card.deserialize line}
     self.new cards
   end
 
   def scores
-    @cards.hash {|card| card.score}
+    @cards.map {|card| card.score}
   end
 
   def scratchcards_generated_by_card(card)
@@ -57,7 +57,7 @@ class Cards
     if score > 0
       sub_cards = @cards.filter {|sub_card| sub_card.id > card.id and sub_card.id <= card.id + score }
       ret += sub_cards
-                  .hash {|sub_card| scratchcards_generated_by_card(sub_card)}
+                  .map {|sub_card| scratchcards_generated_by_card(sub_card)}
                   .flatten
     end
     @scratchcards_generated_by_card_cache[card.id] = ret
diff --git a/src/advent/day5.rb b/src/advent/day5.rb
index 994a7da..fc233ec 100644
--- a/src/advent/day5.rb
+++ b/src/advent/day5.rb
@@ -8,13 +8,25 @@ class WeirMapRange
   end
 
   def includes_source?(source)
-    @source <= source and source <= (@source + @range_length)
+    @source <= source and source < (@source + @range_length)
+  end
+
+  def includes_destination?(destination)
+    @destination <= destination and destination < (@destination + @range_length)
+  end
+
+  def source_for_destination(destination)
+    destination + @source - @destination
   end
 
   def destination_for_source(source)
     @destination + (source - @source)
   end
 
+  def critical_points
+    [@source - 1, @source, @source +  @range_length,  @source +  @range_length + 1]
+  end
+
   def self.deserialize(ser)
     parts = ser.strip.split(/\s+/).map {|p| p.to_i}
     self.new parts[0], parts[1], parts[2]
@@ -30,6 +42,15 @@ class WeirdMap
     @weird_map_ranges = weird_map_ranges
   end
 
+  def preimage_of(destination)
+    @weird_map_ranges.each do |wmr|
+      if wmr.includes_destination? destination
+        return wmr.source_for_destination destination
+      end
+    end
+    destination
+  end
+
   def [](source)
     @weird_map_ranges.each do |wmr|
       if wmr.includes_source? source
@@ -45,6 +66,12 @@ class WeirdMap
        .map {|line| WeirMapRange.deserialize line}
     self.new wmr
   end
+
+  def critical_points
+    @weird_map_ranges.map {|r| r.critical_points} .flatten
+  end
+
+
 end
 
 
@@ -66,6 +93,14 @@ class TodoMap
     @hash[source]
   end
 
+  def critical_points
+    @hash.critical_points
+  end
+
+  def preimage_of(value)
+    @hash.preimage_of value
+  end
+
   attr_accessor :from
   attr_accessor :to
   attr_accessor :hash
@@ -98,12 +133,86 @@ class PlanningMaps
   attr_accessor :seeds
 end
 
+class PlanningMapsWithSeedRanges
+  def initialize(seed_ranges, toto_maps)
+    @seed_ranges = seed_ranges
+    @toto_maps = toto_maps
+  end
+
+  def [](source)
+    ret = source
+    @toto_maps.each {|tm| ret = tm[ret]}
+    ret
+  end
+
+  def self.deserialize_seed_ranges(ser_arr)
+    ser_arr.each_slice(2).map {|start, length| (start...(start + length))}
+  end
+
+  def self.deserialize(ser)
+    blocks = ser.strip.split(/^$/)
+    seeds = blocks[0].split(" ")[(1..)].map {|s| s.to_i}
+    toto_maps = blocks[(1..)].map {|b| TodoMap.deserialize b}
+    self.new(self.deserialize_seed_ranges(seeds), toto_maps)
+  end
+
+  def _preimage_of(value, weird_maps)
+    ret = value
+    weird_maps.each do |weird_map|
+      ret = weird_map.preimage_of ret
+    end
+    ret
+  end
+
+  def _critical_points_of(idx)
+    @toto_maps[idx].critical_points.map {|p| _preimage_of(p, @toto_maps[0...idx])}
+  end
+
+  def critical_points
+    (0...@toto_maps.length).map {|idx| _critical_points_of idx}.flatten.uniq.sort
+  end
+
+  def critical_points_in_range(seed_range)
+    underlying_critical_points = critical_points
+    (underlying_critical_points + [seed_range.min, seed_range.max]).filter {|p| seed_range.include? p}
+  end
+
+  def min_of_seed_range(seed_range)
+    cpts = critical_points_in_range(seed_range)
+    cpts.map {|s| self[s]}.min
+  end
+
+  def all_seeds
+    @seed_ranges.map {|r| r.to_a}.flatten
+  end
+
+  def min_destinations
+    @seed_ranges.map  {|seed_range| min_of_seed_range seed_range}.min
+  end
+
+  def min_destinations_brute_force
+    all_seeds.map {|s| self[s]}.min
+  end
+
+  def seed_of(destination)
+    all_seeds.each do |s|
+      if self[s] == destination
+        return s
+      end
+    end
+  end
+
+  attr_accessor :seed_ranges
+end
+
 
 if __FILE__ == $0
   input_file_name = File.join(File.dirname(__FILE__), "day_5_input.txt")
   input_content = File.open(input_file_name).read
   pms = PlanningMaps.deserialize input_content
+  pmswsr = PlanningMapsWithSeedRanges.deserialize input_content
 
   puts "Solution to part 1: #{pms.min_destinations}"
+  puts "Solution to part 2: #{pmswsr.min_destinations}"
 
 end
diff --git a/src/advent/day5_test.rb b/src/advent/day5_test.rb
index c64d03f..0d7eacb 100644
--- a/src/advent/day5_test.rb
+++ b/src/advent/day5_test.rb
@@ -12,6 +12,29 @@ class TestWeirMapRange < Test::Unit::TestCase
     assert_equal 52, wmr.source
     assert_equal 2, wmr.range_length
   end
+
+  def test_happy_path
+    wmr = WeirMapRange.deserialize "37 52 2"
+    assert_false wmr.includes_destination? 36
+    assert_true wmr.includes_destination? 37
+    assert_true wmr.includes_destination? 38
+    assert_false wmr.includes_destination? 39
+
+
+    assert_false wmr.includes_source? 51
+    assert_true wmr.includes_source? 52
+    assert_true wmr.includes_source? 53
+    assert_false wmr.includes_source? 54
+
+    [51, 52, 53, 54].each do |source|
+      assert_equal(source, wmr.source_for_destination(wmr.destination_for_source(source)))
+    end
+
+    [36,37,38,39].each do |destination|
+      assert_equal(destination, wmr.destination_for_source(wmr.source_for_destination(destination)))
+    end
+
+  end
 end
 
 
@@ -91,6 +114,62 @@ humidity-to-location map:
 
   def test_day_4_part_1
     pms = PlanningMaps.deserialize @@easy_input
-    assert_equal 2, pms.min_destinations
+    assert_equal 35, pms.min_destinations
   end
+end
+
+class TestPlanningMapsWithSeedRanges < Test::Unit::TestCase
+
+  @@easy_input = "seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+temperature-to-humidity map:
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4"
+
+  def test_deserialization
+    pms = PlanningMapsWithSeedRanges.deserialize @@easy_input
+    expt = (79..92).to_a + (55..67).to_a
+    assert_equal(expt, pms.seed_ranges.map {|r| r.to_a} .flatten)
+  end
+
+  def test_brute_force
+    pms = PlanningMapsWithSeedRanges.deserialize @@easy_input
+    assert_equal 46, pms.min_destinations_brute_force
+    assert_equal( 82, pms.seed_of(46))
+  end
+
+  def test_day_5_part_2
+    pms = PlanningMapsWithSeedRanges.deserialize @@easy_input
+    assert_equal 46, pms.min_destinations
+  end
+
+
 end
\ No newline at end of file