From fe5ee7bc16e82baf63c16620b7362731c175ce5b Mon Sep 17 00:00:00 2001
From: Anna Wiggins <annabunches@gmail.com>
Date: Fri, 11 Dec 2020 10:19:50 +0000
Subject: [PATCH] Day 10, first half.

---
 2020/day10.go | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 2020/day10.go

diff --git a/2020/day10.go b/2020/day10.go
new file mode 100644
index 0000000..49ab39e
--- /dev/null
+++ b/2020/day10.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func getMax(values map[int]bool) int {
+	max := 0
+	for value, _ := range values {
+		if value > max {
+			max = value
+		}
+	}
+
+	return max
+}
+
+func main() {
+	// step := os.Args[1]
+	values := fileutils.InputParserIntMap(os.Args[2])
+
+	diffMap := make(map[int]int)
+
+	device := getMax(values) + 3
+	values[device] = true
+
+	diff := 0
+	for i := 0; i < device; i++ {
+		// increment diff, make sure we haven't broken the chain
+		// Note that we're actually logically checking the joltage at i+1
+		// but that serves us well here
+		diff++
+		if diff > 3 {
+			log.Panicf("Diff too big, bailing.")
+		}
+
+		// if we have a device at this joltage, register and reset count
+		if values[i+1] {
+			diffMap[diff]++
+			diff = 0
+		}
+	}
+	fmt.Println(diffMap[1] * diffMap[3])
+}