From 2dd05efae2849b76c6e0d6505706a5f08045008f Mon Sep 17 00:00:00 2001
From: alexchao26 <alexchaoo@gmail.com>
Date: Sun, 27 Dec 2020 20:30:40 -0500
Subject: [PATCH] 2015-day23: an actually easy assembly computer

---
 2015/day23/main.go      | 75 +++++++++++++++++++++++++++--------------
 2015/day23/main_test.go | 29 +++++-----------
 2 files changed, 58 insertions(+), 46 deletions(-)

diff --git a/2015/day23/main.go b/2015/day23/main.go
index 4901f3c..7d4c01f 100644
--- a/2015/day23/main.go
+++ b/2015/day23/main.go
@@ -15,32 +15,57 @@ func main() {
 	flag.Parse()
 	fmt.Println("Running part", part)
 
-	if part == 1 {
-		ans := part1(util.ReadFile("./input.txt"))
-		util.CopyToClipboard(fmt.Sprintf("%v", ans))
-		fmt.Println("Output:", ans)
-	} else {
-		ans := part2(util.ReadFile("./input.txt"))
-		util.CopyToClipboard(fmt.Sprintf("%v", ans))
-		fmt.Println("Output:", ans)
+	ans := simpleAssemblyComputer(util.ReadFile("./input.txt"), part)
+	fmt.Println("Output:", ans)
+}
+
+func simpleAssemblyComputer(input string, part int) int {
+	instructions := strings.Split(input, "\n")
+	var index int
+
+	registers := map[string]int{}
+	if part == 2 {
+		registers["a"] = 1
 	}
-}
 
-func part1(input string) int {
-	parsed := parseInput(input)
-	_ = parsed
-
-	return 0
-}
-
-func part2(input string) int {
-	return 0
-}
-
-func parseInput(input string) (ans []int) {
-	lines := strings.Split(input, "\n")
-	for _, l := range lines {
-		ans = append(ans, cast.ToInt(l))
+	for index < len(instructions) {
+		parts := strings.Split(instructions[index], " ")
+		switch parts[0] {
+		case "hlf":
+			reg := parts[1]
+			registers[reg] /= 2
+			index++
+		case "tpl":
+			reg := parts[1]
+			registers[reg] *= 3
+			index++
+		case "inc":
+			reg := parts[1]
+			registers[reg]++
+			index++
+		case "jmp":
+			diff := cast.ToInt(parts[1])
+			index += diff
+		case "jie":
+			reg := strings.Trim(parts[1], ",")
+			diff := cast.ToInt(parts[2])
+			if registers[reg]%2 == 0 {
+				index += diff
+			} else {
+				index++
+			}
+		case "jio":
+			reg := strings.Trim(parts[1], ",")
+			diff := cast.ToInt(parts[2])
+			if registers[reg] == 1 {
+				index += diff
+			} else {
+				index++
+			}
+		default:
+			panic("unhandled instruction type: " + parts[0])
+		}
 	}
-	return ans
+
+	return registers["b"]
 }
diff --git a/2015/day23/main_test.go b/2015/day23/main_test.go
index 22a4487..3fa3d98 100644
--- a/2015/day23/main_test.go
+++ b/2015/day23/main_test.go
@@ -2,37 +2,24 @@ package main
 
 import (
 	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
 )
 
-func Test_part1(t *testing.T) {
+func Test_simpleAssemblyComputer(t *testing.T) {
 	tests := []struct {
 		name  string
 		input string
+		part  int
 		want  int
 	}{
-		// {"actual", util.ReadFile("input.txt"), ACTUAL_ANSWER},
+		{"actual", util.ReadFile("input.txt"), 1, 307},
+		{"actual", util.ReadFile("input.txt"), 2, 160},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if got := part1(tt.input); got != tt.want {
-				t.Errorf("part1() = %v, want %v", got, tt.want)
-			}
-		})
-	}
-}
-
-func Test_part2(t *testing.T) {
-	tests := []struct {
-		name  string
-		input string
-		want  int
-	}{
-		// {"actual", util.ReadFile("input.txt"), ACTUAL_ANSWER},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got := part2(tt.input); got != tt.want {
-				t.Errorf("part2() = %v, want %v", got, tt.want)
+			if got := simpleAssemblyComputer(tt.input, tt.part); got != tt.want {
+				t.Errorf("simpleAssemblyComputer() = %v, want %v", got, tt.want)
 			}
 		})
 	}