Add test: Sujiko.

sujiko_simetric: 4 guesses.

Note that the puzzle on Wikipedia does not specify the initial board
configuration and is not unique.

tests/sujiko.rs

@@ -0,0 +1,67 @@
+//! Sujiko.
+//!
+//! https://en.wikipedia.org/wiki/Sujiko
+//! https://www.simetric.co.uk/sujiko/index.htm
+
+extern crate puzzle_solver;
+
+use puzzle_solver::{Puzzle,Solution,Val,VarToken};
+
+const SIZE: usize = 3;
+type Board = [[Val; SIZE]; SIZE];
+
+fn make_sujiko(board: &Board, tl: Val, tr: Val, bl: Val, br: Val)
+        -> (Puzzle, Vec<Vec<VarToken>>) {
+    let mut sys = Puzzle::new();
+    let vars = sys.new_vars_with_candidates_2d(3, 3, &[1,2,3,4,5,6,7,8,9]);
+
+    sys.all_different(vars.iter().flat_map(|it| it));
+
+    sys.equals(tl, vars[0][0] + vars[0][1] + vars[1][0] + vars[1][1]);
+    sys.equals(tr, vars[0][1] + vars[0][2] + vars[1][1] + vars[1][2]);
+    sys.equals(bl, vars[1][0] + vars[1][1] + vars[2][0] + vars[2][1]);
+    sys.equals(br, vars[1][1] + vars[1][2] + vars[2][1] + vars[2][2]);
+
+    sys.equals(tl + tr + bl + br - (1..(9 + 1)).sum::<Val>(),
+            vars[0][1] + vars[1][0] + 3 * vars[1][1] + vars[1][2] + vars[2][1]);
+
+    for y in 0..SIZE {
+        for x in 0..SIZE {
+            let value = board[y][x];
+            if value != 0 {
+                sys.set_value(vars[y][x], value);
+            }
+        }
+    }
+
+    (sys, vars)
+}
+
+fn print_sujiko(dict: &Solution, vars: &Vec<Vec<VarToken>>) {
+    for y in 0..SIZE {
+        for x in 0..SIZE {
+            print!(" {}", dict[vars[y][x]]);
+        }
+        println!();
+    }
+}
+
+fn verify_sujiko(dict: &Solution, vars: &Vec<Vec<VarToken>>, expected: &Board) {
+    for y in 0..SIZE {
+        for x in 0..SIZE {
+            assert_eq!(dict[vars[y][x]], expected[y][x]);
+        }
+    }
+}
+
+#[test]
+fn sujiko_simetric() {
+    let puzzle   = [ [ 6,0,9 ], [ 0,0,0 ], [ 5,0,0 ] ];
+    let expected = [ [ 6,2,9 ], [ 8,1,3 ], [ 5,4,7 ] ];
+
+    let (mut sys, vars) = make_sujiko(&puzzle, 17, 15, 18, 15);
+    let dict = sys.solve_unique().expect("solution");
+    print_sujiko(&dict, &vars);
+    verify_sujiko(&dict, &vars, &expected);
+    println!("sujiko_simetric: {} guesses", sys.num_guesses());
+}