Logic puzzle

puzzle.go

// Solve this logic puzzle:
// https://xmonader.github.io/prolog/2018/12/21/solving-murder-prolog.html

package main

import (
	"fmt"

	"github.com/unixpickle/approb"
)

const (
	Bathroom = iota
	DiningRoom
	Kitchen
	LivingRoom
	Pantry
	Study
)

const (
	George = iota
	John
	Robert
	Barbara
	Christine
	Yolanda
)

const (
	Bag = iota
	Firearm
	Gas
	Knife
	Poison
	Rope
)

type Configuration struct {
	People  []int
	Weapons []int
}

func main() {
	for people := range approb.Perms(6) {
		for weapons := range approb.Perms(6) {
			cfg := &Configuration{people, weapons}
			if !clue1(cfg) || !clue2(cfg) || !clue3(cfg) || !clue4(cfg) || !clue5(cfg) ||
				!clue6(cfg) || !clue7(cfg) || !clue8(cfg) || !clue9(cfg) {
				continue
			}
			fmt.Println("person,weapon:", cfg.People[Pantry], cfg.Weapons[Pantry])
		}
	}
}

func clue1(cfg *Configuration) bool {
	return isMan(cfg.People[Kitchen]) && (cfg.Weapons[Kitchen] == Knife || cfg.Weapons[Kitchen] == Gas)
}

func clue2(cfg *Configuration) bool {
	if cfg.People[Study] == Barbara {
		return cfg.People[Bathroom] == Yolanda
	} else if cfg.People[Study] == Yolanda {
		return cfg.People[Bathroom] == Barbara
	} else {
		return false
	}
}

func clue3(cfg *Configuration) bool {
	bagRoom := indexOf(cfg.Weapons, Bag)
	if cfg.People[bagRoom] == Barbara || cfg.People[bagRoom] == George {
		return false
	}
	return bagRoom != Bathroom && bagRoom != DiningRoom
}

func clue4(cfg *Configuration) bool {
	if cfg.Weapons[Study] != Rope {
		return false
	}
	return !isMan(cfg.People[Study])
}

func clue5(cfg *Configuration) bool {
	return cfg.People[LivingRoom] == John || cfg.People[LivingRoom] == George
}

func clue6(cfg *Configuration) bool {
	return cfg.Weapons[DiningRoom] != Knife
}

func clue7(cfg *Configuration) bool {
	return cfg.People[Study] != Yolanda && cfg.People[Pantry] != Yolanda
}

func clue8(cfg *Configuration) bool {
	firearmRoom := indexOf(cfg.Weapons, Firearm)
	return cfg.People[firearmRoom] == George
}

func clue9(cfg *Configuration) bool {
	return cfg.Weapons[Pantry] == Gas
}

func isMan(person int) bool {
	return person < 3
}

func indexOf(l []int, x int) int {
	for i, y := range l {
		if y == x {
			return i
		}
	}
	panic("unreachable")
}