adventofcode/2022/day17/main.go

package main

import (
	"fmt"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := h.StdinToString()
	rocks := [][]h.Coordinate{
		{{X: 0, Y: 0}, {X: 1, Y: 0}, {X: 2, Y: 0}, {X: 3, Y: 0}},
		{{X: 1, Y: 2}, {X: 0, Y: 1}, {X: 1, Y: 1}, {X: 2, Y: 1}, {X: 1, Y: 0}},
		{{X: 2, Y: 2}, {X: 2, Y: 1}, {X: 0, Y: 0}, {X: 1, Y: 0}, {X: 2, Y: 0}},
		{{X: 0, Y: 3}, {X: 0, Y: 2}, {X: 0, Y: 1}, {X: 0, Y: 0}},
		{{X: 0, Y: 1}, {X: 1, Y: 1}, {X: 0, Y: 0}, {X: 1, Y: 0}},
	}
	grid := map[h.Coordinate]struct{}{}
	move := func(rock []h.Coordinate, delta h.Coordinate) bool {
		nrock := make([]h.Coordinate, len(rock))
		for i, p := range rock {
			p = p.Add(delta)
			if _, ok := grid[p]; ok || p.X < 0 || p.X >= 7 || p.Y < 0 {
				return false
			}
			nrock[i] = p
		}
		copy(rock, nrock)
		return true
	}
	cache := map[[2]int][]int{}

	height, jet := 0, 0
	for i := 0; i < 1000000000000; i++ {
		if i == 2022 {
			fmt.Println("# Part 1")
			fmt.Println(height)
			fmt.Println()
		}
		k := [2]int{i % len(rocks), jet}
		if c, ok := cache[k]; ok {
			if n, d := 1000000000000-i, i-c[0]; n%d == 0 {
				fmt.Println("# Part 2")
				fmt.Println(height + n/d*(height-c[1]))
				break
			}
		}
		cache[k] = []int{i, height}

		rock := []h.Coordinate{}
		for _, p := range rocks[i%len(rocks)] {
			rock = append(rock, p.Add(h.Coordinate{X: 2, Y: height + 3}))
		}
		for {
			move(rock, h.Coordinate{X: int(inp[jet]) - int('='), Y: 0})
			jet = (jet + 1) % len(inp)

			if !move(rock, h.Coordinate{X: 0, Y: -1}) {
				for _, p := range rock {
					grid[p] = struct{}{}
					if p.Y+1 > height {
						height = p.Y + 1
					}
				}
				break
			}
		}
	}
}