From f0c7f9815e620e0be5fbbf5a87f490bdf477c32a Mon Sep 17 00:00:00 2001
From: efim <efim.nefedov@nordigy.ru>
Date: Fri, 8 Dec 2023 06:57:24 +0000
Subject: [PATCH] day8, example

---
 day8/dayEight.go | 102 +++++++++++++++++++++++++++++++++++++++++++++++
 day8/example1    |   9 +++++
 day8/example2    |   5 +++
 main.go          |   7 ++--
 4 files changed, 120 insertions(+), 3 deletions(-)
 create mode 100644 day8/dayEight.go
 create mode 100644 day8/example1
 create mode 100644 day8/example2

diff --git a/day8/dayEight.go b/day8/dayEight.go
new file mode 100644
index 0000000..15d2a47
--- /dev/null
+++ b/day8/dayEight.go
@@ -0,0 +1,102 @@
+package day8
+
+import (
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+)
+
+func Run() int {
+	fmt.Print("hello day 8")
+	filename := "day8/example1"
+	net, path := Read(filename)
+	fmt.Printf("got %+v and %+v\n",net, path)
+	result := TraverseNetwork(net, path)
+	return result
+}
+
+func TraverseNetwork(net Network, path Path) int {
+	stepsNum := 0
+
+	curNode := net.Nodes["AAA"]
+	for curNode.Name != "ZZZ" {
+		direction := path.next()
+		var nextNodeName string
+		switch direction {
+		case 'L':
+			nextNodeName = curNode.Left
+		case 'R':
+			nextNodeName = curNode.Right
+		}
+		nextNode, found := net.Nodes[nextNodeName]
+		if !found {
+			panic(fmt.Sprintf("at step %d instruction %s from node %+v results in not found next node %s",
+				stepsNum, string(direction), curNode, nextNodeName))
+		}
+		curNode = nextNode
+
+		stepsNum += 1
+	}
+
+	return stepsNum
+}
+
+func Read(filename string) (Network, Path) {
+	net := Network{
+		Nodes: make(map[string]Node),
+	}
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Sprintln("error reading file ", filename))
+	}
+	lines := strings.Split( string(bytes), "\n")
+	path := Path{
+		Instruction: strings.TrimSpace( lines[0] ),
+	}
+
+	netDescriptions := lines[2:]
+	re := regexp.MustCompile(`(?P<NAME>\D{3}) = \((?P<LEFT>\D{3}), (?P<RIGHT>\D{3})\)`)
+	nameIndex := re.SubexpIndex("NAME")
+	leftIndex := re.SubexpIndex("LEFT")
+	rightIndex := re.SubexpIndex("RIGHT")
+	for _, line := range netDescriptions {
+		if line == "" {
+			continue
+		}
+		match := re.FindStringSubmatch(line)
+		if match == nil {
+			panic(fmt.Sprintln("error finding match in string : ", line))
+		}
+		node := Node{
+			Name: match[nameIndex],
+			Left: match[leftIndex],
+			Right: match[rightIndex],
+		}
+		net.Nodes[node.Name] = node
+	}
+
+	return net, path
+}
+
+type Node struct {
+	Name string
+	Left, Right string
+}
+
+type Network struct {
+	Nodes map[string]Node
+}
+
+type Path struct {
+	Instruction string
+	curStep int
+}
+func (p *Path)next() rune {
+	curInstruction := p.Instruction[p.curStep]
+	p.curStep += 1
+	if p.curStep == len(p.Instruction) {
+		p.curStep = 0
+	}
+	return rune(curInstruction)
+}
diff --git a/day8/example1 b/day8/example1
new file mode 100644
index 0000000..9029a1b
--- /dev/null
+++ b/day8/example1
@@ -0,0 +1,9 @@
+RL
+
+AAA = (BBB, CCC)
+BBB = (DDD, EEE)
+CCC = (ZZZ, GGG)
+DDD = (DDD, DDD)
+EEE = (EEE, EEE)
+GGG = (GGG, GGG)
+ZZZ = (ZZZ, ZZZ)
diff --git a/day8/example2 b/day8/example2
new file mode 100644
index 0000000..7d1b58d
--- /dev/null
+++ b/day8/example2
@@ -0,0 +1,5 @@
+LLR
+
+AAA = (BBB, BBB)
+BBB = (AAA, ZZZ)
+ZZZ = (ZZZ, ZZZ)
diff --git a/main.go b/main.go
index a561580..3bdcc98 100644
--- a/main.go
+++ b/main.go
@@ -3,11 +3,12 @@ package main
 import (
 	"log"
 
-	"sunshine.industries/aoc2023/day7"
+	"sunshine.industries/aoc2023/day8"
 )
 
 func main() {
 	log.Print("> starting run:")
-	result := day7.Run()
-	log.Printf("day7 result: %d\n****\n", result)
+	result := day8.Run()
+	log.Printf("day8 result: %d\n****\n", result)
+
 }