From 42b6f2b511e1d7bbe580d33f04e296cc17144b71 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Wed, 22 Dec 2021 09:33:50 -0800
Subject: [PATCH] 2021 Day 22 Part 1

---
 2021/day22/main.go | 82 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 2021/day22/main.go

diff --git a/2021/day22/main.go b/2021/day22/main.go
new file mode 100644
index 0000000..bf60801
--- /dev/null
+++ b/2021/day22/main.go
@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/jdkaplan/advent-of-code/aoc"
+)
+
+func main() {
+	lines := aoc.Input().ReadLines("day22.txt")
+	steps := parseInput(lines)
+	fmt.Println(part1(steps))
+}
+
+func parseInput(lines []string) (steps []Step) {
+	for _, line := range lines {
+		steps = append(steps, NewStep(line))
+	}
+	return
+}
+
+func part1(steps []Step) int {
+	r := make(Reactor)
+	r.Initialize(steps)
+	return r.CountOn()
+}
+
+type Step struct {
+	op     string
+	x1, x2 int
+	y1, y2 int
+	z1, z2 int
+}
+
+func NewStep(line string) (s Step) {
+	aoc.MustScan(
+		line,
+		"%s x=%d..%d,y=%d..%d,z=%d..%d",
+		&s.op, &s.x1, &s.x2, &s.y1, &s.y2, &s.z1, &s.z2,
+	)
+	return
+}
+
+type Cell struct{ x, y, z int }
+
+type Reactor map[Cell]bool
+
+func (r Reactor) Initialize(steps []Step) {
+	for _, s := range steps {
+		on := s.op == "on"
+		for x := max(-50, s.x1); x <= min(50, s.x2); x++ {
+			for y := max(-50, s.y1); y <= min(50, s.y2); y++ {
+				for z := max(-50, s.z1); z <= min(50, s.z2); z++ {
+					r[Cell{x, y, z}] = on
+				}
+			}
+		}
+	}
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func (r Reactor) CountOn() (count int) {
+	for _, on := range r {
+		if on {
+			count++
+		}
+	}
+	return
+}