aoc-2022/day2/day2.go

package day2

import (
	"fmt"
	"strings"
)

type Solver struct {
	rounds []*Round
}

type ActionType int

const (
	Rock ActionType = iota
	Paper
	Scissors
)

func (a ActionType) Score() int {
	m := map[ActionType]int{Rock: 1, Paper: 2, Scissors: 3}
	return m[a]
}

func NewAction(s string) ActionType {
	switch s {
	case "A", "X":
		return Rock
	case "B", "Y":
		return Paper
	case "C", "Z":
		return Scissors
	}
	panic(fmt.Sprintf("Unhandled action type: %s", s))
}

type Result int

const (
	Win Result = iota
	Loss
	Draw
)

func NewDesiredResult(s string) Result {
	return map[string]Result{"X": Loss, "Y": Draw, "Z": Win}[s]
}

func (r Result) Score() int {
	return map[Result]int{Win: 6, Draw: 3, Loss: 0}[r]
}

type Round struct {
	OpponentAction, OwnAction ActionType
	DesiredResult             Result
}

func (r Round) Score() int {
	var result Result
	switch {
	case r.OwnAction == r.OpponentAction:
		result = Draw
	case r.OwnAction == Rock && r.OpponentAction == Scissors:
		result = Win
	case r.OwnAction == Paper && r.OpponentAction == Rock:
		result = Win
	case r.OwnAction == Scissors && r.OpponentAction == Paper:
		result = Win
	case r.OwnAction == Rock && r.OpponentAction == Paper:
		result = Loss
	case r.OwnAction == Paper && r.OpponentAction == Scissors:
		result = Loss
	case r.OwnAction == Scissors && r.OpponentAction == Rock:
		result = Loss
	}
	return result.Score() + r.OwnAction.Score()
}

func (s *Solver) ParseInput(input []string) {
	s.rounds = make([]*Round, len(input))

	for i, line := range input {
		split := strings.Split(line, " ")
		s.rounds[i] = &Round{
			OpponentAction: NewAction(split[0]),
			OwnAction:      NewAction(split[1]),
			DesiredResult:  NewDesiredResult(split[1]),
		}
	}
}

func (s *Solver) SolvePart1() any {
	return s.score()
}

func (s *Solver) SolvePart2() any {
	for _, r := range s.rounds {
		switch {
		case r.DesiredResult == Draw:
			r.OwnAction = r.OpponentAction

		case r.OpponentAction == Rock && r.DesiredResult == Win:
			r.OwnAction = Paper
		case r.OpponentAction == Rock && r.DesiredResult == Loss:
			r.OwnAction = Scissors

		case r.OpponentAction == Paper && r.DesiredResult == Win:
			r.OwnAction = Scissors
		case r.OpponentAction == Paper && r.DesiredResult == Loss:
			r.OwnAction = Rock

		case r.OpponentAction == Scissors && r.DesiredResult == Win:
			r.OwnAction = Rock
		case r.OpponentAction == Scissors && r.DesiredResult == Loss:
			r.OwnAction = Paper
		}
	}

	return s.score()
}

func (s *Solver) score() int {
	score := 0
	for _, s := range s.rounds {
		score += s.Score()
	}
	return score
}