Create: 0036-valid-sudoku.dart

Author: NikSWE

dart/0036-valid-sudoku.dart

@@ -0,0 +1,31 @@
+// As the board size is fixed
+// it will result in the following
+// Time Complexity: O(1)
+// Space Complexity: O(1)
+
+class Solution {
+  bool isValidSudoku(List<List<String>> board) {
+    var rows = List.filled(9, 0);
+    var cols = List.filled(9, 0);
+    var grids = List.filled(9, 0);
+
+    for (int r = 0; r < 9; r++) {
+      for (int c = 0; c < 9; c++) {
+        if (board[r][c] == ".") continue;
+
+        var idx = int.parse(board[r][c]) - 1;
+
+        if (rows[r] & 1 << idx != 0) return false;
+        rows[r] |= 1 << idx;
+
+        if (cols[c] & 1 << idx != 0) return false;
+        cols[c] |= 1 << idx;
+
+        if (grids[r ~/ 3 * 3 + c ~/ 3] & 1 << idx != 0) return false;
+        grids[r ~/ 3 * 3 + c ~/ 3] |= 1 << idx;
+      }
+    }
+
+    return true;
+  }
+}