From 56cd171588f5a245c79d438014abda52faf2e2b2 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Fri, 11 Dec 2020 17:30:31 -0500
Subject: [PATCH] day ten, part one works, part two doesn't

---
 10/main.go | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 10/main.go

diff --git a/10/main.go b/10/main.go
new file mode 100644
index 0000000..5eb8196
--- /dev/null
+++ b/10/main.go
@@ -0,0 +1,117 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strconv"
+)
+
+func main() {
+	partOne()
+	partTwo()
+}
+
+// Find a chain that uses all of your adapters to connect the charging outlet to your device's built-in adapter
+// and count the joltage differences between the charging outlet, the adapters, and your device.
+// What is the number of 1-jolt differences multiplied by the number of 3-jolt differences?
+
+func partOne() {
+	f, _ := os.Open("input")
+	reader := bufio.NewReader(f)
+	scanner := bufio.NewScanner(reader)
+
+	// wall
+	adapters := []int{0}
+
+	// load
+	for scanner.Scan() {
+		line := scanner.Text()
+		i, _ := strconv.Atoi(line)
+		adapters = append(adapters, i)
+	}
+
+	// sort
+	sort.Slice(adapters, func(i, j int) bool {
+		return adapters[i] < adapters[j]
+	})
+
+	// device
+	adapters = append(adapters, adapters[len(adapters)-1]+3)
+
+	one := 0
+	three := 0
+
+	// count gaps
+	for i, j := range adapters {
+		if i < len(adapters)-1 {
+			if adapters[i+1]-j == 3 {
+				three = three + 1
+			} else if adapters[i+1]-j == 1 {
+				one = one + 1
+			}
+		}
+	}
+
+	fmt.Println(three * one)
+}
+
+// You glance back down at your bag and try to remember why you brought so many adapters; there must be more than a trillion valid ways to arrange them!
+// Surely, there must be an efficient way to count the arrangements.
+// What is the total number of distinct ways you can arrange the adapters to connect the charging outlet to your device?
+
+func partTwo() {
+	f, _ := os.Open("input")
+	reader := bufio.NewReader(f)
+	scanner := bufio.NewScanner(reader)
+
+	// wall
+	adapters := []int{0}
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		i, _ := strconv.Atoi(line)
+		adapters = append(adapters, i)
+	}
+
+	// sort
+	sort.Slice(adapters, func(i, j int) bool {
+		return adapters[i] < adapters[j]
+	})
+
+	// device
+	adapters = append(adapters, adapters[len(adapters)-1]+3)
+
+	combinations := 1
+	ones := 0
+	three := 0
+
+	// count gaps
+	for i, j := range adapters {
+		if i < len(adapters)-1 {
+			if adapters[i+1]-j == 1 {
+				// small steps...
+				ones = ones + 1
+			} else if adapters[i+1]-j == 3 {
+				combinations = combinations + 1
+				if ones == 2 {
+					combinations = combinations * 1
+				}
+				if ones == 3 {
+					combinations = combinations * 2
+				}
+				if ones == 4 {
+					combinations = combinations * 4
+				}
+				if ones == 5 {
+					combinations = combinations * 7
+				}
+				ones = 0
+				three = three + 1
+			}
+		}
+	}
+
+	fmt.Println(adapters, combinations)
+}