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main.go
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main.go
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package main
import (
"fmt"
"math"
"github.com/jdrst/adventofgo/util"
)
func main() {
fmt.Printf("First part: %v\n", partOne(util.ReadFile("input.txt")))
fmt.Printf("Second part: %v\n", partTwo(util.ReadFile("input.txt")))
}
type trajectory struct {
yTrajectory, time int
}
func partOne(file util.File) int {
lines := file.AsLines()
var xmin, xmax, ymin, ymax int
fmt.Sscanf(string(lines[0]), "target area: x=%d..%d, y=%d..%d", &xmin, &xmax, &ymin, &ymax)
possibleYs := []trajectory{}
next:
for traj := ymin; traj < util.Abs(ymin); traj++ {
curr := traj
if curr <= ymax && curr >= ymin {
possibleYs = append(possibleYs, trajectory{yTrajectory: traj, time: 0})
}
for t := 1; ; t++ {
curr += traj - t
if curr < ymin {
continue next
}
if curr <= ymax && curr >= ymin {
possibleYs = append(possibleYs, trajectory{yTrajectory: traj, time: t})
}
}
}
maxY := math.MinInt
for _, t := range possibleYs {
for traj := 0; traj <= xmax; traj++ {
curr := traj
dx := traj
for i := 0; i < t.time; i++ {
dx--
if dx == 0 {
break
}
curr += dx
}
if curr <= xmax && curr >= xmin {
highest := highestPoint(t.yTrajectory)
if highest > maxY {
maxY = highest
}
}
}
}
return maxY
}
func partTwo(file util.File) int {
lines := file.AsLines()
var xmin, xmax, ymin, ymax int
fmt.Sscanf(string(lines[0]), "target area: x=%d..%d, y=%d..%d", &xmin, &xmax, &ymin, &ymax)
possibleYs := []trajectory{}
next:
for traj := ymin; traj < util.Abs(ymin); traj++ {
curr := traj
if curr <= ymax && curr >= ymin {
possibleYs = append(possibleYs, trajectory{yTrajectory: traj, time: 0})
}
for t := 1; ; t++ {
curr += traj - t
if curr < ymin {
continue next
}
if curr <= ymax && curr >= ymin {
possibleYs = append(possibleYs, trajectory{yTrajectory: traj, time: t})
}
}
}
unique := map[util.Point]bool{}
for _, t := range possibleYs {
for traj := 0; traj <= xmax; traj++ {
curr := traj
dx := traj
for i := 1; i <= t.time; i++ {
dx--
if dx == 0 {
break
}
curr += dx
}
if curr <= xmax && curr >= xmin {
unique[util.Point{X: traj, Y: t.yTrajectory}] = true
}
}
}
return len(unique)
}
func highestPoint(y int) int {
return (y * (y + 1)) / 2
}