From 57bfcebc3ec1e3bc43d30156ebc6c1f575e2b210 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Sun, 1 Dec 2019 22:20:41 -0800
Subject: [PATCH] 2019: Day 2 Part 1

---
 2019/day2/input    |  1 +
 2019/day2/part1.rb | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 2019/day2/input
 create mode 100644 2019/day2/part1.rb

diff --git a/2019/day2/input b/2019/day2/input
new file mode 100644
index 0000000..c54d3aa
--- /dev/null
+++ b/2019/day2/input
@@ -0,0 +1 @@
+1,0,0,3,1,1,2,3,1,3,4,3,1,5,0,3,2,10,1,19,2,9,19,23,2,13,23,27,1,6,27,31,2,6,31,35,2,13,35,39,1,39,10,43,2,43,13,47,1,9,47,51,1,51,13,55,1,55,13,59,2,59,13,63,1,63,6,67,2,6,67,71,1,5,71,75,2,6,75,79,1,5,79,83,2,83,6,87,1,5,87,91,1,6,91,95,2,95,6,99,1,5,99,103,1,6,103,107,1,107,2,111,1,111,5,0,99,2,14,0,0
diff --git a/2019/day2/part1.rb b/2019/day2/part1.rb
new file mode 100644
index 0000000..2bca6fa
--- /dev/null
+++ b/2019/day2/part1.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+program = File.read(File.join(__dir__, 'input'))
+
+def run(mem)
+  pc = 0
+  loop do
+    case mem[pc]
+    when 1
+      r1, r2, r3 = mem[pc+1], mem[pc+2], mem[pc+3]
+      mem[r3] = mem[r1] + mem[r2]
+      pc += 4
+    when 2
+      r1, r2, r3 = mem[pc+1], mem[pc+2], mem[pc+3]
+      mem[r3] = mem[r1] * mem[r2]
+      pc += 4
+    when 99
+      return
+    else
+      raise StandardError, "unexpected opcode: #{opcode}"
+    end
+  end
+end
+
+mem = program.split(',').map(&:to_i)
+mem[1] = 12
+mem[2] = 2
+run(mem)
+puts mem[0]