2018 Day 06 Complete

2018/day06/day06.go

@@ -0,0 +1,185 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const MaxInt = int(^uint(0) >> 1)
+
+func main() {
+	inp := StdinToStringSlice()
+	start(inp)
+	part1()
+	part2()
+}
+
+var points []RegionPos
+var boundaries []RegionPos
+var allPoints []RegionPos
+var maxX, maxY, minX, minY int
+
+func start(inp []string) {
+	maxX, maxY = 0, 0
+	minX, minY = MaxInt, MaxInt
+
+	for _, v := range inp {
+		pts := strings.Split(v, ", ")
+		x, y := Atoi(pts[0]), Atoi(pts[1])
+		p := RegionPos{x: x, y: y}
+		points = append(points, p)
+		if x < minX {
+			minX = x
+		}
+		if x > maxX {
+			maxX = x
+		}
+		if y < minY {
+			minY = y
+		}
+		if y > maxY {
+			maxY = y
+		}
+	}
+	// Find the points that are the closest to the boundaries
+	for x := minX; x <= maxX; x++ {
+		boundaries = append(boundaries, *NewRegionPos(x, minY))
+		boundaries = append(boundaries, *NewRegionPos(x, maxY))
+	}
+	for y := minY; y <= maxY; y++ {
+		boundaries = append(boundaries, *NewRegionPos(minX, y))
+		boundaries = append(boundaries, *NewRegionPos(maxX, y))
+	}
+	for i := range boundaries {
+		closest := boundaries[i].findClosest(points)
+		if len(closest) == 1 {
+			for j := range points {
+				if points[j].x == closest[0].x && points[j].y == closest[0].y {
+					points[j].ignored = true
+				}
+			}
+		} else {
+			boundaries[i].ignored = true
+		}
+	}
+}
+
+func part1() {
+	for x := minX; x <= maxX; x++ {
+		for y := minY; y <= maxY; y++ {
+			p := NewRegionPos(x, y)
+			closest := p.findClosest(points)
+			if len(closest) == 1 {
+				c := closest[0]
+				for i := range points {
+					if points[i].ignored {
+						continue
+					}
+					if points[i].x == c.x && points[i].y == c.y {
+						points[i].regionSize++
+						break
+					}
+				}
+			}
+		}
+	}
+	var largestSize int
+	for _, v := range points {
+		if !v.ignored {
+			if v.regionSize > largestSize {
+				largestSize = v.regionSize
+			}
+		}
+	}
+	fmt.Println("= Part 1 =")
+	fmt.Println(largestSize)
+}
+
+func part2() {
+	minDistance := 10000
+
+	var regionCount int
+	for y := minY - minDistance; y <= maxY+minDistance; y++ {
+		for x := minX - minDistance; x <= maxX+minDistance; x++ {
+			p := NewRegionPos(x, y)
+			if p.sumOfDistances(minDistance, points) < minDistance {
+				regionCount++
+			}
+		}
+	}
+	fmt.Println("= Part 2 =")
+	fmt.Println(regionCount)
+}
+
+func manhattanDistance(x1, y1, x2, y2 int) int {
+	return int(math.Abs(float64(x1)-float64(x2)) + math.Abs(float64(y1)-float64(y2)))
+}
+
+type RegionPos struct {
+	x, y       int
+	regionSize int
+	closestPos *RegionPos
+	ignored    bool
+}
+
+func NewRegionPos(x, y int) *RegionPos {
+	b := &RegionPos{}
+	b.x = x
+	b.y = y
+	return b
+}
+
+func (p *RegionPos) distanceToPos(o *RegionPos) int {
+	return manhattanDistance(p.x, p.y, o.x, o.y)
+}
+
+func (b *RegionPos) sumOfDistances(d int, list []RegionPos) int {
+	var ret int
+	for _, p := range list {
+		ret += b.distanceToPos(&p)
+	}
+	return ret
+}
+
+func (b *RegionPos) findClosest(list []RegionPos) []RegionPos {
+	var ret []RegionPos
+	minD := MaxInt
+	for _, p := range list {
+		test := b.distanceToPos(&p)
+		if test < minD {
+			minD = test
+			ret = ret[:0]
+			ret = append(ret, p)
+		} else if test == minD {
+			ret = append(ret, p)
+		}
+	}
+	return ret
+}
+
+func (b *RegionPos) string() string {
+	return fmt.Sprintf("%d;%d", b.x, b.y)
+}
+
+func StdinToStringSlice() []string {
+	var input []string
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		input = append(input, scanner.Text())
+	}
+	return input
+}
+
+func Atoi(i string) int {
+	var ret int
+	var err error
+	if ret, err = strconv.Atoi(i); err != nil {
+		log.Fatal("Invalid Atoi")
+	}
+	return ret
+}