advent-of-code/day14/main.go

package main

import (
	"bufio"
	_ "embed"
	"fmt"
	"strings"

	aoc "go.sour.is/advent-of-code-2023"
	"golang.org/x/exp/maps"
)

// var log = aoc.Log

func main() { aoc.MustResult(aoc.Runner(run)) }

type result struct {
	valuePT1 int
	valuePT2 int
}

func (r result) String() string { return fmt.Sprintf("%#v", r) }

func run(scan *bufio.Scanner) (*result, error) {
	var maplist []Map
	var m Map

	for scan.Scan() {
		text := scan.Text()
		if len(text) == 0 {
			maplist = append(maplist, m)
			m = Map{}
		}

		m = append(m, []rune(text))
	}
	maplist = append(maplist, m)

	score1 := 0
	for _, m := range maplist {
		m = aoc.Transpose(reverse(m))
		m.Sort()
		score1 += m.Score()
	}

	score2 := 0
	type record [5]int
	var current record
	memo := make(map[record]int)

	for _, m := range maplist {
		// fmt.Println(m)

		m = aoc.Transpose(reverse(m))

		for i := 0; i < 1_000_000_000; i++ {
			m, current = cycle(m)

			v, ok := memo[current]
			if ok && v > 1 {
				counts := aoc.Reduce(
					func(i int, v int, counts [3]int) [3]int {
						counts[v]++
						return counts
					}, [3]int{}, maps.Values(memo)...)

				// fmt.Println(i, counts)
				i = 1_000_000_000 - (1_000_000_000-counts[0]-counts[1])%counts[2]
				clear(memo)
			}
			memo[current] += 1
			// fmt.Println(i, current, v)
		}
		score2 += m.Score()
	}

	return &result{valuePT1: score1, valuePT2: score2}, nil
}

type Map [][]rune

func (m Map) String() string {
	var buf strings.Builder
	for _, row := range m {
		buf.WriteString(string(row))
		buf.WriteRune('\n')
	}
	buf.WriteRune('\n')

	return buf.String()
}
func (m *Map) Sort() {
	if m == nil {
		return
	}
	for _, row := range *m {
		base := 0
		for i, r := range row {
			if r == '#' {
				base = i + 1
				continue
			}
			if r == 'O' {
				if base < i {
					row[base], row[i] = row[i], row[base]
				}
				base++
			}
		}
	}
}
func (m *Map) Score() int {
	if m == nil {
		return 0
	}

	sum := 0
	max := len(*m)
	for _, row := range *m {
		for i, r := range row {
			if r == 'O' {
				sum += max - i
			}
		}
	}
	return sum
}

func reverse(m Map) Map {
	for _, row := range m {
		aoc.Reverse(row)
	}
	return m
}
func cycle(m Map) (Map, [5]int) {
	var current [5]int

	m.Sort()
	current[0] = m.Score()

	m = aoc.Transpose(reverse(m))
	m.Sort()
	current[1] = m.Score()

	m = aoc.Transpose(reverse(m))
	m.Sort()
	current[2] = m.Score()

	m = aoc.Transpose(reverse(m))
	m.Sort()
	current[3] = m.Score()

	m = aoc.Transpose(reverse(m))
	current[4] = m.Score()

	return m, current
}