day16, example two

day16/floorWillBeLava.go

@@ -3,6 +3,7 @@ package day16
 import (
 	"fmt"
 	"log"
+	"math"
 	"os"
 	"strings"
 	"sync"
@@ -11,13 +12,63 @@ import (
 func Run() int {
 	fmt.Println("hello from day 16")
 	log.Println("starting")
-	field := ReadField("day16/input")
-	fmt.Println(field.String())
-	field.StartTraversal()
+	filename := "day16/example"
+	field := ReadField(filename)
+	startPoints := StartPoints(&field)
 
-	fmt.Println(field.ShowEnergyzed())
+	var startPointsWaitGroup sync.WaitGroup
+	startPointsWaitGroup.Add(len(startPoints))
 
-	return field.CountEnergized()
+	results := make(chan int)
+
+	go func() {
+		startPointsWaitGroup.Wait()
+		close(results)
+	}()
+
+	for _, start := range startPoints {
+		go func(start MovementPoint) {
+			cleanField := ReadField(filename)
+			cleanField.StartTraversal(start)
+			thisResult := cleanField.CountEnergized()
+			results <- thisResult
+			startPointsWaitGroup.Done()
+		}(start)
+	}
+
+	max := math.MinInt
+	for energized := range results {
+		if energized > max {
+			max = energized
+			log.Println("found new max: ", max)
+		}
+	}
+
+	// fmt.Println(field.String())
+	// field.StartTraversal()
+
+	// fmt.Println(field.ShowEnergyzed())
+
+	return max
+}
+
+func StartPoints(f *Field) []MovementPoint {
+	result := make([]MovementPoint, 0)
+
+	for rowNum, row := range f.cells {
+		result = append(result,
+			MovementPoint{Row: rowNum, Col: 0, Direction: Rightward},
+			MovementPoint{Row: rowNum, Col: len(row) - 1, Direction: Leftward})
+	}
+
+	for colNum, _ := range f.cells[0] {
+		result = append(result,
+			MovementPoint{Row: 0, Col: colNum, Direction: Downward},
+			MovementPoint{Row: len(f.cells) - 1, Col: colNum, Direction: Upward})
+
+	}
+
+	return result
 }
 
 // have shared field
@@ -53,7 +104,7 @@ type Field struct {
 	cells [][]*Cell
 }
 
-func (f *Field)isValid(mp MovementPoint) bool {
+func (f *Field) isValid(mp MovementPoint) bool {
 	if mp.Row < 0 || mp.Col < 0 {
 		return false
 	}
@@ -84,7 +135,7 @@ func ReadField(filename string) Field {
 	return result
 }
 
-func (f *Field)String() string {
+func (f *Field) String() string {
 	result := "\n"
 	for _, row := range f.cells {
 		for _, cell := range row {
@@ -95,7 +146,7 @@ func (f *Field)String() string {
 	return result
 }
 
-func (f *Field)ShowEnergyzed() string {
+func (f *Field) ShowEnergyzed() string {
 	result := "\n"
 	for _, row := range f.cells {
 		for _, cell := range row {
@@ -117,14 +168,11 @@ type MovementPoint struct {
 	Direction Direction
 }
 
-func (f *Field)StartTraversal() {
+func (f *Field) StartTraversal(startPoint MovementPoint) {
 	reportedVisits := make(chan MovementPoint)
 	var wg sync.WaitGroup
 
 	go f.RecordVisits(reportedVisits)
-	startPoint := MovementPoint {
-		Row: 0, Col: 0, Direction: Rightward,
-	}
 	wg.Add(1)
 	go f.TraverseFrom(startPoint, reportedVisits, &wg)
 
@@ -132,7 +180,7 @@ func (f *Field)StartTraversal() {
 	close(reportedVisits)
 }
 
-func (f *Field)CountEnergized() (result int) {
+func (f *Field) CountEnergized() (result int) {
 	for _, row := range f.cells {
 		for _, cell := range row {
 			if len(cell.KnownBeams) > 0 {
@@ -143,7 +191,7 @@ func (f *Field)CountEnergized() (result int) {
 	return
 }
 
-func (f *Field)RecordVisits(reportedPoints <-chan MovementPoint) {
+func (f *Field) RecordVisits(reportedPoints <-chan MovementPoint) {
 	for point := range reportedPoints {
 		cell := f.cells[point.Row][point.Col]
 		log.Printf("recording visit %+v to %+v at row %d col %d\n", point, cell, point.Row, point.Col)
@@ -154,7 +202,7 @@ func (f *Field)RecordVisits(reportedPoints <-chan MovementPoint) {
 // starting at point, mark as visited
 // move (concurrently if required) into next points
 // ends - when out of the field, or if encountering a cycle
-func (f *Field)TraverseFrom(current MovementPoint, reportVisits chan<- MovementPoint, wg *sync.WaitGroup) {
+func (f *Field) TraverseFrom(current MovementPoint, reportVisits chan<- MovementPoint, wg *sync.WaitGroup) {
 	log.Printf("> starting traverse through %+v", current)
 	if !f.isValid(current) {
 		log.Println("invalid current ", current, " should be impossible")
@@ -204,7 +252,7 @@ func NextPoints(f *Field, current MovementPoint) []MovementPoint {
 
 // value receiver, can safely modify incoming mp
 // doesn't know about Field dimentions
-func (mp MovementPoint)ApplyDirection(d Direction) MovementPoint {
+func (mp MovementPoint) ApplyDirection(d Direction) MovementPoint {
 	switch d {
 	case Upward:
 		mp.Row -= 1