day8, example3

day8/dayEight.go

@@ -2,20 +2,71 @@ package day8
 
 import (
 	"fmt"
+	"log"
 	"os"
 	"regexp"
+	"slices"
 	"strings"
 )
 
 func Run() int {
 	fmt.Print("hello day 8")
-	filename := "day8/input"
+	filename := "day8/example3"
 	net, path := Read(filename)
 	fmt.Printf("got %+v and %+v\n", net, path)
-	result := TraverseNetwork(net, path)
+	result := GhostTraverse(net, path)
 	return result
 }
 
+func GhostTraverse(net Network, path Path) int {
+	stepsNum := 0
+	simultaneousPaths := make([]Node, 0)
+	for nodeName, node := range net.Nodes {
+		if strings.HasSuffix(nodeName, "A") {
+			simultaneousPaths = append(simultaneousPaths, node)
+		}
+	}
+	log.Printf("collected start points: %+v\n", simultaneousPaths)
+
+	// concurrent iteraction
+	for !isGhostWayDone(simultaneousPaths) {
+		direction := path.next()
+		for i, curNode := range simultaneousPaths {
+			simultaneousPaths[i] = getNextNode(net, curNode, direction)
+		}
+		// log.Printf("done step into %+v\n", simultaneousPaths)
+		stepsNum += 1
+	}
+
+	return stepsNum
+}
+
+func isGhostWayDone(simulaneousPath []Node) bool {
+	containsNonZEnding := slices.ContainsFunc(simulaneousPath, func(curNode Node) bool {
+		name := curNode.Name
+		last := name[len(name) - 1]
+		return last != 'Z'
+	})
+	// log.Printf("checking if done for %+v : %t", simulaneousPath, !containsNonZEnding)
+	return !containsNonZEnding
+}
+
+func getNextNode(net Network, curNode Node, direction rune) Node {
+	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("instruction %s from node %+v results in not found next node %s",
+			string(direction), curNode, nextNodeName))
+	}
+	return nextNode
+}
+
 func TraverseNetwork(net Network, path Path) int {
 	stepsNum := 0
 
@@ -92,6 +143,7 @@ type Path struct {
 	Instruction string
 	curStep     int
 }
+
 func (p *Path) next() rune {
 	curInstruction := p.Instruction[p.curStep]
 	p.curStep += 1

day8/example3

@@ -0,0 +1,10 @@
+LR
+
+GGA = (GGB, XXX)
+GGB = (XXX, GGZ)
+GGZ = (GGB, XXX)
+HHA = (HHB, XXX)
+HHB = (HHC, HHC)
+HHC = (HHZ, HHZ)
+HHZ = (HHB, HHB)
+XXX = (XXX, XXX)