feat: day 15 (a + b) in ruby

day15_a.rb

@@ -0,0 +1,5 @@
+line = gets.chomp
+seqs = line.split(',')
+
+ans = seqs.map { |seq| seq.chars.reduce(0) { |acc, e| (17 * (acc + e.ord)) % 256 } }.sum
+puts ans

day15_b.rb

@@ -0,0 +1,20 @@
+line = gets.chomp
+
+ops = line.split(',').map { |seq| /(\w+)([=-])(\d?)/.match(seq)&.captures }.map { |lab, cmd, mp|
+  dst = lab.chars.reduce(0) { |acc, e| (17 * (acc + e.ord)) % 256 }
+  [lab, cmd, mp.to_i, dst]
+}
+
+boxes = Array.new(256) { {} }
+ops.each { |l, c, m, d|
+  case c
+  when '=' then boxes[d][l] = m
+  when '-' then boxes[d].delete(l)
+  end
+}
+
+ans = boxes.each_with_index.map { |box, idx|
+  box.to_a.each_with_index.map { |bx, i| (idx+1) * (i+1) * bx[1] }.sum
+}.sum
+
+puts ans