From 34e58114ead933c7de67d381432756ac945bd719 Mon Sep 17 00:00:00 2001
From: David Wang <millimillenary@gmail.com>
Date: Fri, 24 Feb 2017 07:21:09 +1100
Subject: [PATCH] Add test: Sudoku.

sudoku_hardest: 1850 guesses.
sudoku_wikipedia: no guesswork!
---
 tests/sudoku.rs | 135 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 tests/sudoku.rs

diff --git a/tests/sudoku.rs b/tests/sudoku.rs
new file mode 100644
index 0000000..b2b59d7
--- /dev/null
+++ b/tests/sudoku.rs
@@ -0,0 +1,135 @@
+//! Sudoku.
+//!
+//! https://en.wikipedia.org/wiki/Sudoku
+
+extern crate puzzle_solver;
+
+use puzzle_solver::{Puzzle,Solution,Val,VarToken};
+
+const SQRT_SIZE: usize = 3;
+const SIZE: usize = 9;
+type Board = [[Val; SIZE]; SIZE];
+
+fn make_sudoku(board: &Board) -> (Puzzle, Vec<Vec<VarToken>>) {
+    let mut sys = Puzzle::new();
+    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1,2,3,4,5,6,7,8,9]);
+
+    for y in 0..SIZE {
+        sys.all_different(&vars[y]);
+    }
+
+    for x in 0..SIZE {
+        sys.all_different(vars.iter().map(|row| &row[x]));
+    }
+
+    for block in 0..SIZE {
+        let x0 = SQRT_SIZE * (block % SQRT_SIZE);
+        let y0 = SQRT_SIZE * (block / SQRT_SIZE);
+        sys.all_different((0..SIZE).map(|n|
+                &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
+    }
+
+    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_sudoku(dict: &Solution, vars: &Vec<Vec<VarToken>>) {
+    for y in 0..SIZE {
+        if y % SQRT_SIZE == 0 {
+            println!();
+        }
+
+        for x in 0..SIZE {
+            print!("{}{}",
+                   if x % SQRT_SIZE == 0 { " " } else { "" },
+                   dict[vars[y][x]]);
+        }
+        println!();
+    }
+}
+
+fn verify_sudoku(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 sudoku_hardest() {
+    let puzzle = [
+        [ 8,0,0,  0,0,0,  0,0,0 ],
+        [ 0,0,3,  6,0,0,  0,0,0 ],
+        [ 0,7,0,  0,9,0,  2,0,0 ],
+
+        [ 0,5,0,  0,0,7,  0,0,0 ],
+        [ 0,0,0,  0,4,5,  7,0,0 ],
+        [ 0,0,0,  1,0,0,  0,3,0 ],
+
+        [ 0,0,1,  0,0,0,  0,6,8 ],
+        [ 0,0,8,  5,0,0,  0,1,0 ],
+        [ 0,9,0,  0,0,0,  4,0,0 ] ];
+
+    let expected = [
+        [ 8,1,2,  7,5,3,  6,4,9 ],
+        [ 9,4,3,  6,8,2,  1,7,5 ],
+        [ 6,7,5,  4,9,1,  2,8,3 ],
+
+        [ 1,5,4,  2,3,7,  8,9,6 ],
+        [ 3,6,9,  8,4,5,  7,2,1 ],
+        [ 2,8,7,  1,6,9,  5,3,4 ],
+
+        [ 5,2,1,  9,7,4,  3,6,8 ],
+        [ 4,3,8,  5,2,6,  9,1,7 ],
+        [ 7,9,6,  3,1,8,  4,5,2 ] ];
+
+    let (mut sys, vars) = make_sudoku(&puzzle);
+    let solution = sys.solve_any().expect("solution");
+    print_sudoku(&solution, &vars);
+    verify_sudoku(&solution, &vars, &expected);
+    println!("sudoku_hardest: {} guesses", sys.num_guesses());
+}
+
+#[test]
+fn sudoku_wikipedia() {
+    let puzzle = [
+        [ 5,3,0,  0,7,0,  0,0,0 ],
+        [ 6,0,0,  1,9,5,  0,0,0 ],
+        [ 0,9,8,  0,0,0,  0,6,0 ],
+
+        [ 8,0,0,  0,6,0,  0,0,3 ],
+        [ 4,0,0,  8,0,3,  0,0,1 ],
+        [ 7,0,0,  0,2,0,  0,0,6 ],
+
+        [ 0,6,0,  0,0,0,  2,8,0 ],
+        [ 0,0,0,  4,1,9,  0,0,5 ],
+        [ 0,0,0,  0,8,0,  0,7,9 ] ];
+
+    let expected = [
+        [ 5,3,4,  6,7,8,  9,1,2 ],
+        [ 6,7,2,  1,9,5,  3,4,8 ],
+        [ 1,9,8,  3,4,2,  5,6,7 ],
+
+        [ 8,5,9,  7,6,1,  4,2,3 ],
+        [ 4,2,6,  8,5,3,  7,9,1 ],
+        [ 7,1,3,  9,2,4,  8,5,6 ],
+
+        [ 9,6,1,  5,3,7,  2,8,4 ],
+        [ 2,8,7,  4,1,9,  6,3,5 ],
+        [ 3,4,5,  2,8,6,  1,7,9 ] ];
+
+    let (mut sys, vars) = make_sudoku(&puzzle);
+    let solution = sys.solve_any().expect("solution");
+    print_sudoku(&solution, &vars);
+    verify_sudoku(&solution, &vars, &expected);
+    println!("sudoku_wikipedia: {} guesses", sys.num_guesses());
+}