fix validation of 3x3 blocks

src/sudoku/validator.rs

@@ -22,7 +22,7 @@ pub fn is_solution(sudoku: &Board) -> bool {
         let mut block_set = 0u16;
         for j in 0..9 {
             let tmp = block_set;
-            block_set ^= 1 << sudoku[i / 3 * 3 + i % 3][j / 3 * 3 + j % 3];
+            block_set ^= 1 << sudoku[i / 3 * 3 + j / 3][i % 3 * 3 + j % 3];
             if block_set < tmp {
                 return false;
             }

src/tests/validator.rs

@@ -47,3 +47,19 @@ fn invalid_unfinished() {
     ];
     assert!(!is_solution(&board));
 }
+
+#[test]
+fn invalid_blocks_wrong() {
+    let board = [
+        [5, 6, 9, 3, 7, 8, 1, 2, 4],
+        [7, 4, 3, 1, 2, 9, 6, 5, 8],
+        [4, 5, 1, 6, 8, 2, 9, 7, 3],
+        [9, 8, 6, 7, 4, 5, 3, 1, 2],
+        [6, 3, 7, 2, 5, 1, 4, 8, 9],
+        [8, 9, 2, 4, 1, 3, 7, 6, 5],
+        [3, 1, 8, 5, 6, 4, 2, 9, 7],
+        [2, 7, 4, 8, 9, 6, 5, 3, 1],
+        [1, 2, 5, 9, 3, 7, 8, 4, 6],
+    ];
+    assert!(!is_solution(&board));
+}