Add Crystal solution to day 13

day13.cr

@@ -0,0 +1,110 @@
+require "advent"
+INPUT = input(2022, 13).lines
+
+class Tree
+  property value : Int32?
+  property values : Array(Tree)?
+
+  def initialize(@value, @values)
+  end
+
+  def to_s(io)
+    if mine = value
+      io << "value: " << mine
+    elsif mine = values
+      io << "values: "
+      mine.each do |v|
+        io << "("
+        v.to_s io
+        io << ")"
+      end
+    end
+  end
+
+  def compare(other : Tree)
+    if mine = value
+      if yours = other.value
+        return (mine - yours).sign
+      end
+    end
+
+    if mine = values
+      if yours = other.values
+        mine.size.times do |i|
+          return 1 unless i < yours.size # Shorter list smaller
+          comp = mine[i].compare yours[i]
+          return comp if comp != 0
+        end
+        return mine.size == yours.size ? 0 : -1 # Shorter list smaller
+      end
+    end
+
+    if mine = value
+      return Tree.new(nil, [self]).compare(other)
+    elsif yours = other.value
+      return compare(Tree.new(nil, [other]))
+    end
+    return 0
+  end
+end
+
+def tree(i)
+  Tree.new(i, nil)
+end
+
+def list(is : Array(Int32))
+  Tree.new(nil, is.map { |it| tree(it) })
+end
+
+def list(is : Array(Tree))
+  Tree.new(nil, is)
+end
+
+def parse(string)
+  stack = [[] of Tree]
+  current = nil
+  string.as(String).each_char do |c|
+    if c == '['
+      stack << [] of Tree
+    elsif c.alphanumeric?
+      if current.nil?
+        current = c.to_i32
+      else
+        current = current * 10 + c.to_i32
+      end
+    elsif c == ','
+      if num = current
+        stack.last << tree(num)
+        current = nil
+      end
+    elsif c == ']'
+      if num = current
+        stack.last << tree(num)
+        current = nil
+      end
+      new_tree = Tree.new(nil, stack.pop)
+      stack.last << new_tree
+    end
+  end
+  return stack[0][0]
+end
+
+puts parse("[[10,1,2],[],[]]")
+total = 0
+INPUT.in_groups_of(3).each_with_index do |group, i|
+  t1 = parse(group[0])
+  t2 = parse(group[1])
+  cmp = t1.compare t2
+  total += (i+1) if cmp != 1
+end
+puts total
+
+trees = INPUT.reject { |it| it.empty? }.map { |it| parse(it) }
+d1 = parse("[[2]]")
+d2 = parse("[[6]]")
+trees << d1
+trees << d2
+trees.sort! do |l, r|
+  l.compare r
+end
+puts (trees.index!(d1)+1)*(trees.index!(d2)+1)