Clean up some solutions.

day6.cr

@@ -2,20 +2,12 @@ require "advent"
 INPUT = input(2020, 6).split("\n\n")
 
 def part1
-  input = INPUT.clone
-  answers = input.map do |i|
-    i.chars.uniq!.count &.ascii_letter?
-  end
-  puts answers.sum
+  INPUT.sum &.chars.uniq!.count(&.ascii_letter?)
 end
 
 def part2
-  input = INPUT.clone
-  sol = input.map do |i|
-    i.split("\n").reject(&.empty?).map(&.chars.to_set).reduce { |s1, s2| s1 & s2 }
-  end
-  puts(sol.map(&.size).sum)
+  INPUT.sum &.lines.map(&.chars.to_set).intersect.size
 end
 
-part1
-part2
+puts part1
+puts part2

day7.cr

@@ -0,0 +1,45 @@
+require "advent"
+
+INPUT = input(2020, 7).lines.map(&.chomp).map do |s|
+  data = s.match(/^([a-z ]+) bags contain (.*).$/).not_nil!
+  contents = data[2].split(", ").compact_map do |s|
+    s.match(/(\d+) (.*) bags?/).try { |m| {m[1].to_i32, m[2]} }
+  end
+  {data[1], contents}
+end
+
+def build_graph(input)
+  gr = Graph(String).new
+  seen = Set(String).new
+  input.each do |i|
+    seen << i[0]
+    i[1].each do |to|
+      n, m = to
+      gr.add_edge(i[0], m, n)
+    end
+  end
+  {seen, gr}
+end
+
+def part1
+  seen, gr = build_graph(INPUT)
+  seen.count do |s|
+    gr.find_path(s, "shiny gold") && s != "shiny gold"
+  end
+end
+
+def count_bags(gr, current)
+  return 1 unless es = gr.@edges[current]?
+  1 + es.sum do |e|
+    t, k = e
+    k * count_bags(gr, t)
+  end
+end
+
+def part2
+  seen, gr = build_graph(INPUT)
+  count_bags(gr, "shiny gold") - 1
+end
+
+puts part1
+puts part2

day8.cr

@@ -0,0 +1,44 @@
+require "advent"
+INPUT = input(2020, 8).lines.map do |s|
+  code, int = s.split(" ")
+  {code, int.to_i32}
+end
+
+def run(prog)
+  acc = 0
+  pc = 0
+  visited = Set(Int32).new
+  loop do
+    return {:term, acc} if pc >= prog.size
+    return {:inf, acc} if visited.includes? pc
+      
+    visited << pc
+    code, int = prog[pc]
+    case code
+    when "acc"
+      acc += int
+    when "jmp"
+      pc += int - 1
+    end
+    pc += 1
+  end
+end
+
+def part1
+  run(INPUT)[1]
+end
+
+def part2
+  jnp = INPUT.find_indices { |e| e[0] == "jmp" || e[0] == "nop" }
+  jnp.each do |i|
+    prog = INPUT.clone
+    op, int = prog[i]
+    prog[i] = {op.tr("jmpnop", "nopjmp"), int}
+
+    code, acc = run(prog)
+    return acc if code == :term
+  end
+end
+
+puts part1
+puts part2