Solutions for day 10.

2018/day10-1.go

@@ -1,8 +1,6 @@
 package main
 
 import (
-	"fmt"
-
 	"internal/day10"
 	"internal/util"
 )
@@ -11,27 +9,21 @@ func main() {
 	data := util.ReadInput()
 	points := day10.ParseInput(data)
 
-	i := 0 // debug
+	lowest := day10.CalculateRange(points)
 	for {
 		for _, point := range points {
 			point.Move()
 		}
 
-		groups := day10.GroupPoints(points)
+		newRange := day10.CalculateRange(points)
-		if groups != nil {
+		if newRange < lowest {
-			for _, group := range groups {
+			lowest = newRange
-				day10.DrawPoints(group)
+		} else {
-				fmt.Println()
+			for _, point := range points {
+				point.Reverse()
 			}
+			day10.DrawPoints(points)
 			return
 		}
-
-		// debug
-		i++
-		if i > 100000 {
-			fmt.Println("oops")
-			return
-		}
-		// end debug
 	}
 }

2018/day10-2.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+
+	"internal/day10"
+	"internal/util"
+)
+
+func main() {
+	data := util.ReadInput()
+	points := day10.ParseInput(data)
+
+	lowest := day10.CalculateRange(points)
+	i := 0
+	for {
+		for _, point := range points {
+			point.Move()
+		}
+
+		newRange := day10.CalculateRange(points)
+		if newRange < lowest {
+			lowest = newRange
+		} else {
+			fmt.Println(i)
+			return
+		}
+
+		i++
+	}
+}

2018/internal/day10/groups.go

@@ -1,5 +1,11 @@
+// Unused solution: yes, this is a SECOND failed solution. Left here as a testament
+// to... something. The actual solution uses CalculateRange from point.go
 package day10
 
+import (
+	"sort"
+)
+
 // GroupPoints creates groups of points, then sorts them and returns the sorted list
 // A 'group' is a series of points that are adjacent to each other.
 // If this function finds any non-adjacent points, it returns nil.
@@ -36,7 +42,12 @@ func GroupPoints(points []*Point) [][]*Point {
 		groups = append(groups, group)
 	}
 
-	// TODO: sort the groups
+	// sort the groups
+	sort.Slice(groups[:], func(i, j int) bool {
+		xMin1, _, _, _ := findBounds(groups[i])
+		xMin2, _, _, _ := findBounds(groups[j])
+		return xMin1 < xMin2
+	})
 
 	return groups
 }

2018/internal/day10/point.go

@@ -14,6 +14,16 @@ func (p *Point) Move() {
 	p.Y += p.Yv
 }
 
+func (p *Point) Reverse() {
+	p.X -= p.Xv
+	p.Y -= p.Yv
+}
+
+func CalculateRange(points []*Point) int {
+	xMin, xMax, yMin, yMax := findBounds(points)
+	return xMax - xMin + yMax - yMin
+}
+
 func DrawPoints(points []*Point) {
 	pointArr := makeBuffer(points)
 
@@ -33,7 +43,11 @@ func DrawPoints(points []*Point) {
 // findBounds returns xMin, xMax, yMin, and yMax from the provided points.
 func findBounds(points []*Point) (int, int, int, int) {
 	// find min and max values
-	var xMin, xMax, yMin, yMax int
+	xMin := points[0].X
+	xMax := points[0].X
+	yMin := points[0].Y
+	yMax := points[0].Y
+
 	for _, point := range points {
 		if point.X < xMin {
 			xMin = point.X
@@ -54,6 +68,7 @@ func findBounds(points []*Point) (int, int, int, int) {
 
 func makeBuffer(points []*Point) [][]byte {
 	xMin, xMax, yMin, yMax := findBounds(points)
+
 	// get the total magnitude; we'll do adjustments later
 	xRange := xMax - xMin
 	yRange := yMax - yMin