2017 Day 20 Complete!

2017/day20/day20.go

@@ -0,0 +1,215 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var particles map[int]*Particle
+var confidenceThreshold int
+
+func main() {
+	inp := StdinToStrings()
+	particles = make(map[int]*Particle)
+	for i := range inp {
+		particles[i] = NewParticle(inp[i], i)
+	}
+	confidenceThreshold = 1000
+	doPart := 2
+	if len(os.Args) > 1 {
+		if os.Args[1] == "-1" {
+			doPart = 1
+		}
+	}
+	switch doPart {
+	case 1:
+		part1(inp)
+	case 2:
+		part2(inp)
+	}
+}
+
+func part1(inp []string) {
+	var ticks, confidence, last int
+	cPart := -1
+	for {
+		cDist := 10000000000
+		ticks++
+		for i := range particles {
+			particles[i].Tick()
+			if particles[i].GetDistance() < cDist {
+				cPart = i
+				cDist = particles[i].GetDistance()
+			}
+		}
+		if cPart == last {
+			confidence++
+		} else {
+			confidence = 0
+			last = cPart
+		}
+		if confidence >= confidenceThreshold {
+			break
+		}
+	}
+	fmt.Println("After", ticks, "the closest is", cPart)
+}
+
+func part2(inp []string) {
+	var ticks, lastNum, confidence int
+	for {
+		ticks++
+		for i := range particles {
+			particles[i].Tick()
+		}
+		var collisions []int
+		for k1, v1 := range particles {
+			for k2, v2 := range particles {
+				if k1 == k2 {
+					continue
+				}
+				if v1.Collides(v2) {
+					collisions = AddToSlice(collisions, k1)
+					collisions = AddToSlice(collisions, k2)
+					break
+				}
+			}
+		}
+		for i := len(collisions) - 1; i >= 0; i-- {
+			delete(particles, collisions[i])
+		}
+		if len(particles) == lastNum {
+			confidence++
+		} else {
+			confidence = 0
+			lastNum = len(particles)
+		}
+		if confidence >= confidenceThreshold {
+			break
+		}
+	}
+	fmt.Println("After", ticks, "there are", len(particles), "particles left")
+}
+
+func AddToSlice(sl []int, v int) []int {
+	for i := range sl {
+		if sl[i] == v {
+			return sl
+		}
+	}
+	sl = append(sl, v)
+	return sl
+}
+
+type Coordinate struct {
+	X, Y, Z int
+}
+
+func NewCoordinate(inp string) Coordinate {
+	inp = inp[1 : len(inp)-1]
+	pts := strings.Split(inp, ",")
+	px, py, pz := Atoi(pts[0]), Atoi(pts[1]), Atoi(pts[2])
+	return Coordinate{X: px, Y: py, Z: pz}
+}
+
+func (c *Coordinate) toString() string {
+	return fmt.Sprintf("<%d,%d,%d>", c.X, c.Y, c.Z)
+}
+
+type Particle struct {
+	Index        int
+	Position     Coordinate
+	Velocity     Coordinate
+	Acceleration Coordinate
+
+	LastPosition Coordinate
+}
+
+func NewParticle(inp string, idx int) *Particle {
+	ret := new(Particle)
+	ret.Index = idx
+	pts := strings.Split(inp, " ")
+	for i := range pts {
+		keyVal := strings.Split(pts[i], "=")
+		if keyVal[1][len(keyVal[1])-1] == ',' {
+			keyVal[1] = keyVal[1][:len(keyVal[1])-1]
+		}
+		switch keyVal[0] {
+		case "p":
+			ret.Position = NewCoordinate(keyVal[1])
+		case "v":
+			ret.Velocity = NewCoordinate(keyVal[1])
+		case "a":
+			ret.Acceleration = NewCoordinate(keyVal[1])
+		}
+	}
+	ret.LastPosition = NewCoordinate(ret.Position.toString())
+	return ret
+}
+
+func (p *Particle) Collides(tst *Particle) bool {
+	if p.Position.X == tst.Position.X &&
+		p.Position.Y == tst.Position.Y &&
+		p.Position.Z == tst.Position.Z {
+		return true
+	}
+	return false
+}
+
+func (p *Particle) String() string {
+	return fmt.Sprintf(
+		"p=<%d,%d,%d>, v=<%d,%d,%d>, a=<%d,%d,%d>",
+		p.Position.X, p.Position.Y, p.Position.Z,
+		p.Velocity.X, p.Velocity.Y, p.Velocity.Z,
+		p.Acceleration.X, p.Acceleration.Y, p.Acceleration.Z,
+	)
+}
+
+func (p *Particle) Tick() {
+	p.LastPosition = NewCoordinate(p.Position.toString())
+	p.Velocity.X += p.Acceleration.X
+	p.Velocity.Y += p.Acceleration.Y
+	p.Velocity.Z += p.Acceleration.Z
+	p.Position.X += p.Velocity.X
+	p.Position.Y += p.Velocity.Y
+	p.Position.Z += p.Velocity.Z
+}
+
+func (p *Particle) IsDone() bool {
+	return p.GetDistance() == p.GetLastDistance()
+}
+
+func (p *Particle) GetDistance() int {
+	return GetAbs(p.Position.X) + GetAbs(p.Position.Y) + GetAbs(p.Position.Z)
+}
+
+func (p *Particle) GetLastDistance() int {
+	return int(math.Abs(float64(p.LastPosition.X + p.LastPosition.Y + p.LastPosition.Z)))
+}
+
+func StdinToStrings() []string {
+	var input []string
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		input = append(input, scanner.Text())
+	}
+	return input
+}
+
+func GetAbs(v int) int {
+	return int(math.Abs(float64(v)))
+}
+
+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
+}