adventofcode/2020/day19/main.go

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	fmt.Println("# Day 19")
	fmt.Println()
	inp := h.StdinToStringSlice()
	part := h.OptArgNumber(1, "2")
	solve(inp, h.Atoi(part))
}

var loopingTokens []int
var allTokens map[int]*Token
var totalRules int

/*
 8: 42 | 42 8
11: 42 31 | 42 11 31

Figure out the values of 31 & 42, then see how they
affect things as they repeat

31: 95 7 | 104 130
42: 29 104 | 115 95
*/

func solve(inp []string, part int) {
	allTokens = make(map[int]*Token)
	var section int
	var rules []string
	var messages []string
	for _, v := range inp {
		if v == "" {
			// End of the rules list
			section++
		}
		switch section {
		case 0:
			rules = append(rules, v)
		case 1:
			messages = append(messages, v)
		}
	}
	totalRules = len(rules)
	last := -1
	for RulesSolved() < totalRules && last != RulesSolved() {
		last = RulesSolved()
		for _, v := range rules {
			fmt.Println("Restarting Rules Parsing")
			pts := strings.Split(v, ": ")
			num := h.Atoi(pts[0])
			if part == 2 {
				if num == 8 {
					pts[1] = "42 | 42 8"
				} else if num == 11 {
					pts[1] = "42 31 | 42 11 31"
				}
			}
			if _, ok := allTokens[num]; !ok {
				GenerateToken(num, pts[1])
			}
		}
	}
	if RulesSolved() < totalRules {
		fmt.Println("Unable to solve all rules")
		os.Exit(1)
	}
	fmt.Println("Calculating Answer")
	var matches int
	for _, v := range messages {
		if allTokens[0].Matches(v) {
			matches++
		}
	}
	fmt.Printf("## Part 1\nAnswer: %d\n", matches)
}

// RulesSolved TODO
func RulesSolved() int {
	var ret int
	for k := range allTokens {
		if k >= 0 {
			ret++
		}
	}
	return ret
}

// Token Kinds
const (
	LEAF = iota
	STICK
	BRANCH
)

// Token TODO
type Token struct {
	kind  int
	num   int
	value string
	raw   string

	PartNums []int
	Parts    []*Token

	CachedValues []string
	Loops        bool
}

// GenerateToken TODO
func GenerateToken(num int, raw string) *Token {
	if v, ok := allTokens[num]; ok {
		return v
	}
	t := Token{num: num, raw: raw}
	if raw[0] == '"' {
		t.value = strings.ReplaceAll(raw, "\"", "")
		t.kind = LEAF
	} else {
		if !strings.Contains(raw, "|") {
			t.kind = STICK
			var partTokens []*Token
			pts := strings.Split(raw, " ")
			for k := range pts {
				if pts[k] == "|" {
					continue
				}
				t.PartNums = append(t.PartNums, h.Atoi(pts[k]))
			}
			solved := true
			for k := range t.PartNums {
				if v, ok := allTokens[t.PartNums[k]]; ok || h.IntSliceContains(loopingTokens, t.PartNums[k]) {
					partTokens = append(partTokens, v)
				} else {
					solved = false
					break
				}
			}
			if solved {
				t.Parts = partTokens
			}
		} else {
			t.kind = BRANCH
			pts := strings.Split(raw, " ")
			for k := range pts {
				if pts[k] == "|" {
					continue
				}
				n := h.Atoi(pts[k])
				if n == num {
					if !h.IntSliceContains(loopingTokens, t.num) {
						fmt.Println(num, "IS A LOOPING TOKEN")
						loopingTokens = append(loopingTokens, t.num)
						t.Loops = true
					}
				}
			}
			branches := strings.Split(raw, " | ")
			var partTokens []*Token
			for k, branch := range branches {
				branchID := -(num*1000 + k)
				t.PartNums = append(t.PartNums, branchID)
				p := GenerateToken(branchID, branch)
				if p.Solved() {
					allTokens[branchID] = p
					partTokens = append(partTokens, p)
				} else {
					continue
				}
			}
			solved := true
			for _, bid := range t.PartNums {
				if _, ok := allTokens[bid]; !ok {
					solved = false
					break
				}
			}
			if solved {
				t.Parts = partTokens
			}
		}
	}
	if t.Solved() {
		allTokens[num] = &t
	} else {
		fmt.Println("> Couldn't Solve", num)
	}
	return &t
}

// Solved TODO
func (t *Token) Solved() bool {
	return len(t.Values()) > 0
}

// Values TODO
func (t *Token) Values() []string {
	switch t.kind {
	case LEAF:
		return t.LeafValue()
	case STICK:
		return t.StickValue()
	case BRANCH:
		return t.BranchValue()
	default:
		return []string{}
	}
}

// LeafValue TODO
func (t *Token) LeafValue() []string {
	return []string{t.value}
}

// StickValue TODO
func (t *Token) StickValue() []string {
	if len(t.Parts) < len(t.PartNums) {
		return []string{}
	}
	if len(t.CachedValues) > 0 {
		return t.CachedValues
	}
	var ret []string
	for k := range t.Parts {
		if len(ret) == 0 {
			ret = t.Parts[k].Values()
		} else {
			var newRet []string
			for rk := range ret {
				newRet = append(newRet, h.AppendStrings(ret[rk], t.Parts[k].Values())...)
			}
			ret = newRet
		}
	}
	t.CachedValues = ret
	return ret
}

// BranchValue TODO
func (t *Token) BranchValue() []string {
	if len(t.Parts) < len(t.PartNums) {
		return []string{}
	}
	if len(t.CachedValues) > 0 {
		return t.CachedValues
	}
	var ret []string
	for k := range t.Parts {
		ret = append(ret, t.Parts[k].Values()...)
	}
	t.CachedValues = ret
	return ret
}

// Matches actually tests a message against this token
func (t *Token) Matches(msg string) bool {
	for _, v := range t.Values() {
		if msg == v {
			return true
		}
	}
	return false
}

func (t Token) String() string {
	return fmt.Sprintf("{num:%d, kind:%s, partNums:%v, value:%v}", t.num, KindToString(t.kind), t.PartNums, t.Values())
}

// KindToString TODO
func KindToString(kind int) string {
	switch kind {
	case LEAF:
		return "LEAF"
	case STICK:
		return "STICK"
	case BRANCH:
		return "BRANCH"
	default:
		return "UNKNOWN"
	}
}