Add test: Zebra puzzle (A.K.A. Einstein's riddle).

zebra: 453 guesses.

tests/zebra.rs

@@ -0,0 +1,117 @@
+//! Zebra puzzle (A.K.A. Einstein's riddle).
+//!
+//! https://en.wikipedia.org/wiki/Zebra_Puzzle
+//! https://rosettacode.org/wiki/Zebra_puzzle
+
+#![allow(non_upper_case_globals)]
+
+extern crate puzzle_solver;
+
+use puzzle_solver::Puzzle;
+
+#[derive(Clone,Copy,Debug)]
+enum Nat { Dane, Englishman, German, Norwegian, Swede }
+
+#[derive(Clone,Copy,Debug)]
+enum Col { Blue, Green, Red, White, Yellow }
+
+#[derive(Clone,Copy,Debug)]
+enum Dri { Beer, Coffee, Milk, Tea, Water }
+
+#[derive(Clone,Copy,Debug)]
+enum Smo { Blend, BlueMaster, Dunhill, PallMall, Prince }
+
+#[derive(Clone,Copy,Debug)]
+enum Pet { Bird, Cat, Dog, Fish, Horse }
+
+#[test]
+fn zebra() {
+    use Nat::*; use Col::*; use Dri::*; use Smo::*; use Pet::*;
+
+    // #1: There are five houses.
+    let mut sys = Puzzle::new();
+    let nat_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
+    let col_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
+    let dri_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
+    let smo_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
+    let pet_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
+
+    let nat = |n| nat_var[n as usize];
+    let col = |n| col_var[n as usize];
+    let dri = |n| dri_var[n as usize];
+    let smo = |n| smo_var[n as usize];
+    let pet = |n| pet_var[n as usize];
+
+    sys.all_different(&nat_var);
+    sys.all_different(&col_var);
+    sys.all_different(&dri_var);
+    sys.all_different(&smo_var);
+    sys.all_different(&pet_var);
+
+    // #2: The Englishman lives in the red house.
+    sys.equals(nat(Englishman), col(Red));
+
+    // #3: The Swede has a dog.
+    sys.equals(nat(Swede), pet(Dog));
+
+    // #4: The Dane drinks tea.
+    sys.equals(nat(Dane), dri(Tea));
+
+    // #5: The green house is immediately to the left of the white house.
+    sys.equals(col(Green), col(White) - 1);
+
+    // #6: They drink coffee in the green house.
+    sys.equals(dri(Coffee), col(Green));
+
+    // #7: The man who smokes Pall Mall has birds.
+    sys.equals(smo(PallMall), pet(Bird));
+
+    // #8: In the yellow house they smoke Dunhill.
+    sys.equals(col(Yellow), smo(Dunhill));
+
+    // #9: In the middle house they drink milk.
+    sys.equals(dri(Milk), 3);
+
+    // #10: The Norwegian lives in the first house.
+    sys.equals(nat(Norwegian), 1);
+
+    // #11: The man who smokes Blend lives in the house next to the house with cats.
+    let neighbour11 = sys.new_var_with_candidates(&[-1,1]);
+    sys.equals(smo(Blend), pet(Cat) + neighbour11);
+
+    // #12: In a house next to the house where they have a horse, they smoke Dunhill.
+    let neighbour12 = sys.new_var_with_candidates(&[-1,1]);
+    sys.equals(pet(Horse), smo(Dunhill) + neighbour12);
+
+    // #13: The man who smokes Blue Master drinks beer.
+    sys.equals(smo(BlueMaster), dri(Beer));
+
+    // #14: The German smokes Prince.
+    sys.equals(nat(German), smo(Prince));
+
+    // #15: The Norwegian lives next to the blue house.
+    let neighbour15 = sys.new_var_with_candidates(&[-1,1]);
+    sys.equals(nat(Norwegian), col(Blue) + neighbour15);
+
+    // #16: They drink water in a house next to the house where they smoke Blend.
+    let neighbour16 = sys.new_var_with_candidates(&[-1,1]);
+    sys.equals(dri(Water), smo(Blend) + neighbour16);
+
+    let dict = sys.solve_any().expect("solution");
+
+    let expected = [
+        (Norwegian,  Yellow, Water,  Dunhill,    Cat),
+        (Dane,       Blue,   Tea,    Blend,      Horse),
+        (Englishman, Red,    Milk,   PallMall,   Bird),
+        (German,     Green,  Coffee, Prince,     Fish),
+        (Swede,      White,  Beer,   BlueMaster, Dog) ];
+
+    for &(n,c,d,s,p) in expected.iter() {
+        assert_eq!(dict[nat(n)], dict[col(c)]);
+        assert_eq!(dict[nat(n)], dict[dri(d)]);
+        assert_eq!(dict[nat(n)], dict[smo(s)]);
+        assert_eq!(dict[nat(n)], dict[pet(p)]);
+    }
+
+    println!("zebra: {} guesses", sys.num_guesses());
+}