adventofcode/2023/day14/main.go

package main

import (
	"fmt"

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

func main() {
	inp := h.StdinToStringSlice()
	part1(inp)
	fmt.Println()
	part2(inp)
}

func part1(input []string) {
	m := h.StringSliceToCoordByteMap(input)
	fmt.Println("# Part 1")
	tiltNorth(&m)
	fmt.Println(calcLoad(&m))
}

func part2(input []string) {
	target := 1_000_000_000
	mapCache := make(map[string]int)
	m := h.StringSliceToCoordByteMap(input)
	var i = 0
	var ignoreCache bool
	for ; i <= target; i++ {
		tiltNorth(&m)
		tiltWest(&m)
		tiltSouth(&m)
		tiltEast(&m)
		if !ignoreCache {
			if v, ok := mapCache[m.String()]; ok && i > 200 {
				target = i + (target-v)%(i-v) - 1
				ignoreCache = true
			}
			mapCache[m.String()] = i
		}
	}
	fmt.Println("# Part 2")
	fmt.Println(calcLoad(&m))
}

func c(x, y int) h.Coordinate { return h.Coordinate{X: x, Y: y} }

// m.FindAll returns a slice sorted Left->Right, Top->Bottom
func tiltNorth(m *h.CoordByteMap) {
	rocks := m.FindAll('O')
	for i := range rocks {
		if rocks[i].Y == m.TLY {
			continue
		}
		mv := h.Coordinate{X: rocks[i].X, Y: rocks[i].Y}
		for m.Get(mv.North()) == '.' {
			mv.MoveNorth()
		}
		if !mv.Equals(rocks[i]) {
			m.Put(rocks[i], '.')
			m.Put(mv, 'O')
		}
	}
}
func tiltEast(m *h.CoordByteMap) {
	rocks := m.FindAll('O')
	for i, j := 0, len(rocks)-1; i < j; i, j = i+1, j-1 {
		rocks[i], rocks[j] = rocks[j], rocks[i]
	}
	for i := range rocks {
		if rocks[i].X == m.BRX {
			continue
		}
		mv := h.Coordinate{X: rocks[i].X, Y: rocks[i].Y}
		for m.Get(mv.East()) == '.' {
			mv.MoveEast()
		}
		if !mv.Equals(rocks[i]) {
			m.Put(rocks[i], '.')
			m.Put(mv, 'O')
		}
	}
}
func tiltSouth(m *h.CoordByteMap) {
	rocks := m.FindAll('O')
	for i, j := 0, len(rocks)-1; i < j; i, j = i+1, j-1 {
		rocks[i], rocks[j] = rocks[j], rocks[i]
	}
	for i := range rocks {
		if rocks[i].Y == m.BRY {
			continue
		}
		mv := h.Coordinate{X: rocks[i].X, Y: rocks[i].Y}
		for m.Get(mv.South()) == '.' {
			mv.MoveSouth()
		}
		if !mv.Equals(rocks[i]) {
			m.Put(rocks[i], '.')
			m.Put(mv, 'O')
		}
	}
}
func tiltWest(m *h.CoordByteMap) {
	rocks := m.FindAll('O')
	for i := range rocks {
		if rocks[i].X == m.TLX {
			continue
		}
		mv := h.Coordinate{X: rocks[i].X, Y: rocks[i].Y}
		for m.Get(mv.West()) == '.' {
			mv.MoveWest()
		}
		if !mv.Equals(rocks[i]) {
			m.Put(rocks[i], '.')
			m.Put(mv, 'O')
		}
	}
}

func calcLoad(m *h.CoordByteMap) int {
	var res int
	bot := m.BRY
	rocks := m.FindAll('O')
	for i := range rocks {
		res += (bot - rocks[i].Y) + 1
	}
	return res
}