colors <- c("Red", "Green", "Ivory", "Yellow", "Blue") nationalities <- c("Englishman", "Spaniard", "Ukrainian", "Japanese", "Norwegian") # nolint pets <- c("Dog", "Snails", "Fox", "Horse", "Zebra") drinks <- c("Coffee", "Tea", "Milk", "OrangeJuice", "Water") hobbies <- c("Dancing", "Painting", "Reading", "Football", "Chess") drinks_water <- function() { solution <- solve() solution$Nation[match("Water", solution$Drink)] } owns_zebra <- function() { solution <- solve() solution$Nation[match("Zebra", solution$Pet)] } solve <- function() { # nolint for (nation in permute(nationalities)) { if (nation[1] != "Norwegian") next for (color in permute(colors)) { if (match("Englishman", nation) != match("Red", color)) next if (abs(match("Norwegian", nation) - match("Blue", color)) != 1) next if ((match("Ivory", color) + 1) != match("Green", color)) next for (hobby in permute(hobbies)) { if (match("Painting", hobby) != match("Yellow", color)) next if (match("Chess", hobby) != match("Japanese", nation)) next for (pet in permute(pets)) { if (abs(match("Reading", hobby) - match("Fox", pet)) != 1) next if (abs(match("Painting", hobby) - match("Horse", pet)) != 1) next if (match("Spaniard", nation) != match("Dog", pet)) next if (match("Dancing", hobby) != match("Snails", pet)) next for (drink in permute(drinks)) { if (drink[3] != "Milk") next if (match("Ukrainian", nation) != match("Tea", drink)) next if (match("Green", color) != match("Coffee", drink)) next if (match("Football", hobby) != match("OrangeJuice", drink)) next return( data.frame( Nation = nation, Color = color, hobby = hobby, Pet = pet, Drink = drink ) ) } } } } } stop("Could not find solution") } permute <- function(x) { if (length(x) == 1) { return(list(x)) } result <- list() for (i in seq_along(x)) { sub_perms <- permute(x[-i]) for (sub_perm in sub_perms) { result <- append(result, list(c(x[i], sub_perm))) } } return(result) }