adventofcode/2023/day21/main.go

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package main
import (
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"container/list"
"fmt"
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"image"
"os"
"strings"
)
func main() {
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data, _ := os.ReadFile("input")
answer := solution(data, 64)
fmt.Println("# Part 1")
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fmt.Println(answer[0])
fmt.Println("# Part 2")
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fmt.Println(answer[1])
}
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func solution(data []byte, total_steps int) []int {
lines := strings.Split(strings.TrimSpace(string(data)), "\n")
q := list.New()
symbols := map[image.Point]string{}
for y, line := range lines {
l := strings.TrimSpace(line)
//fmt.Println(len(s))
for x, r := range l {
symbols[image.Point{x, y}] = string(r)
if r == 'S' {
q.PushBack(image.Point{x, y})
}
}
}
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steps := 0
total := 26501365
part_1 := 0
part_2 := 0
directions := []image.Point{
{-1, 0}, {0, -1}, {0, 1}, {1, 0},
}
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polynomial := make([]int, 0)
for steps < total {
new_Q := list.New()
visited := make(map[image.Point]bool)
for q.Len() > 0 {
element := q.Front()
val := element.Value.(image.Point)
q.Remove(element)
x, y := val.X, val.Y
for _, d := range directions {
newPos := image.Point{x + d.X, y + d.Y}
ref := image.Point{((newPos.Y % len(lines)) + len(lines)) % len(lines), ((newPos.X % len(lines)) + len(lines)) % len(lines)}
if symbols[ref] != "#" {
if _, ok := visited[newPos]; !ok {
visited[newPos] = true
new_Q.PushBack(newPos)
}
}
}
}
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steps += 1
q = new_Q //update queue
if steps%(len(lines)) == total%len(lines) {
polynomial = append(polynomial, len(visited))
if len(polynomial) == 3 {
p0 := polynomial[0]
p1 := polynomial[1] - polynomial[0]
p2 := polynomial[2] - polynomial[1]
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part_2 = p0 + (p1 * (total / len(lines))) + ((total/len(lines))*((total/len(lines))-1)/2)*(p2-p1)
break
}
}
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if steps == total_steps {
part_1 = len(visited)
}
}
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return []int{part_1, part_2}
}