Add day 8 solution.

day8.cr

@@ -0,0 +1,84 @@
+require "advent"
+INPUT = input(2020, 8).lines
+
+def part1
+  acc = 0
+  pc = 0
+  visited = Set(Int32).new
+  input = INPUT.clone.map do |s|
+    code, int = s.split(" ")
+    {code, int.to_i32}
+  end
+
+  loop do
+    if visited.includes? pc
+      break
+    end
+    visited << pc
+    code, int = input[pc]
+    case input[pc][0]
+    when "acc"
+      acc += int
+      pc += 1
+    when "jmp"
+      pc += int
+    when "nop"
+      pc += 1
+    end
+  end
+end
+
+def run(prog)
+  acc = 0
+  pc = 0
+  visited = Set(Int32).new
+  loop do
+    if visited.includes? pc
+      return false
+    end
+    return acc if pc >= prog.size
+    visited << pc
+    code, int = prog[pc]
+    case prog[pc][0]
+    when "acc"
+      acc += int
+      pc += 1
+    when "jmp"
+      pc += int
+    when "nop"
+      pc += 1
+    end
+  end
+end
+
+def part2
+  input = INPUT.clone.map do |s|
+    code, int = s.split(" ")
+    {code, int.to_i32}
+  end
+
+  jnp = [] of Int32
+  input.each_with_index do |e, i|
+    op, int = e
+    jnp << i if op == "jmp" || op == "nop"
+  end
+
+  jnp.each do |i|
+    prog = input.clone
+    if prog[i][0] == "jmp"
+      prog[i] = {"nop", prog[i][1]}
+    else
+      prog[i] = {"jmp", prog[i][1]}
+    end
+
+    case i = run(prog)
+    when Bool
+      next
+    when Int32
+      return i
+    end
+  end
+end
+
+puts part1
+puts part2