aoc2023/day-12/one.go

package main

import (
	"fmt"

	log "github.com/sirupsen/logrus"
)

const (
	OPERATIONAL = iota
	DAMAGED
	UNKNOWN
)

var records []record

type record struct {
	format  []int
	springs []spring
}

func newRecord() record {
	return record{}
}

// raw returns the state of all springs for this record as int array
func (r record) raw() []int {
	vals := make([]int, len(r.springs))
	for j, spring := range r.springs {
		vals[j] = spring.state
	}
	return vals
}

type spring struct {
	state int
}

func newSpring(state int) spring {
	return spring{state: state}
}

// tracker keeps track of results for function calls
type tracker struct {
	checked map[string]int
}

func newTracker() tracker {
	return tracker{checked: make(map[string]int)}
}

func (t tracker) add(key string, res int) {
	t.checked[key] = res
}

func validate(springs, format []int) bool {
	return !contains(springs[:format[0]], OPERATIONAL) && (format[0] == len(springs) || springs[format[0]] != DAMAGED)
}

// count returns the number of arrangements possible for a set of springs
func count(springs, format []int) int {
	if len(springs) == 0 {
		if len(format) == 0 {
			return 1
		}
		return 0
	}
	if len(format) == 0 {
		if contains(springs, DAMAGED) {
			return 0
		}
		return 1
	}

	identifier := fmt.Sprintf("%v%v", format, springs)
	if res, ok := fnTracker.checked[fmt.Sprintf("%v%v", format, springs)]; ok {
		log.Debug("returning cached value for ", identifier)
		return res
	}

	result := 0

	if springs[0] == OPERATIONAL || springs[0] == UNKNOWN {
		result += count(springs[1:], format)
	}

	if springs[0] == DAMAGED || springs[0] == UNKNOWN {
		if format[0] < len(springs) && validate(springs, format) {
			result += count(springs[format[0]+1:], format[1:])
		} else if format[0] == len(springs) && validate(springs, format) {
			result += count(springs[format[0]:], format[1:])
		}
	}

	fnTracker.add(identifier, result)
	return result
}

var fnTracker tracker

// one returns the sum of all arrangement counts
func one(lines []string) int {
	parselines(lines)

	fnTracker = newTracker()
	sum := 0
	for _, record := range records {
		raw := record.raw()
		sum += count(raw, record.format)
	}

	return sum
}