2023 Day 01 Part 2 Complete

2023/01/spec/trebuchet_spec.rb

@@ -13,8 +13,21 @@
     EOS
   }
 
+  let(:input2) {
+    <<~EOS
+      two1nine
+      eightwothree
+      abcone2threexyz
+      xtwone3four
+      4nineeightseven2
+      zoneight234
+      7pqrstsixteen
+    EOS
+  }
+
   describe Advent::Trebuchet do
     let(:ad) { Advent::Trebuchet.new(input) }
+    let(:ad2) { Advent::Trebuchet.new(input2) }
 
     describe "#new" do
     end
@@ -28,12 +41,25 @@
         ad = Advent::Trebuchet.new("12abc2")
         expect(ad.nums).to eq([12])
       end
+
+      it "extracts digits as strings" do
+        expect(ad2.nums).to eq([29, 83, 13, 24, 42, 14, 76])
+      end
+
+      it "handles strings with overlapping numbers" do
+        ad = Advent::Trebuchet.new("haseightwoeightwohas")
+        expect(ad.nums).to eq([82])
+      end
     end
 
     context "validation" do
       it "validates part1 examples" do
         expect(ad.sum).to eq(142)
       end
+
+      it "validates part2 examples" do
+        expect(ad2.sum).to eq(281)
+      end
     end
   end
 end

2023/01/trebuchet.rb

@@ -12,11 +12,29 @@ def initialize(input)
       @lines = input.each_line.map(&:strip)
     end
 
+    STRING_TO_NUM = {
+      "one" => 1,
+      "two" => 2,
+      "three" => 3,
+      "four" => 4,
+      "five" => 5,
+      "six" => 6,
+      "seven" => 7,
+      "eight" => 8,
+      "nine" => 9,
+    }
+    START_REGEX = /^.*?(one|two|three|four|five|six|seven|eight|nine|\d)/
+    END_REGEX = /.*(one|two|three|four|five|six|seven|eight|nine|\d)/
+
     def nums
       @nums ||= @lines.map do |line|
-        numbers_in_string = line.scan(/\d/).map(&:to_i)
-        a = numbers_in_string.first
-        b = numbers_in_string.last
+        line.match(START_REGEX)
+        a = $1
+        a = STRING_TO_NUM.has_key?(a) ? STRING_TO_NUM[a] : a.to_i
+        line.match(END_REGEX)
+        b = $1
+        b = STRING_TO_NUM.has_key?(b) ? STRING_TO_NUM[b] : b.to_i
+
         a * 10 + b
       end
     end