From a5b6c520532ea05bd7714efd847bf9e8e7f0d429 Mon Sep 17 00:00:00 2001
From: Quinn <quinnthepigeon@proton.me>
Date: Tue, 29 Jul 2025 11:46:18 +0200
Subject: [PATCH] write code to initialise the sudoku board

---
 src/sudoku.c | 6 ++++++
 src/sudoku.h | 9 +++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/sudoku.c b/src/sudoku.c
index af93562..4b0ebb1 100644
--- a/src/sudoku.c
+++ b/src/sudoku.c
@@ -8,6 +8,12 @@
 
 #include "util/intdef.h"
 
+void sudoku_init(u16 *board) {
+	for (uint i = 0; i < SUDOKU_DEPTH_2; i++) {
+		board[i] |= SUDOKU_ALL & -!board[i];
+	}
+}
+
 void sudoku_solve_step(u16 *board) {
 	u16 bmask[SUDOKU_DEPTH_2]; // board mask
 	memcpy(bmask, board, SUDOKU_DEPTH_2 * 2);
diff --git a/src/sudoku.h b/src/sudoku.h
index 61ed3d8..f42a165 100644
--- a/src/sudoku.h
+++ b/src/sudoku.h
@@ -4,8 +4,9 @@
 
 #include "util/intdef.h"
 
-#define SUDOKU_DEPTH   9                             // defines the "depth" of the puzzle.
-#define SUDOKU_DEPTH_2 (SUDOKU_DEPTH * SUDOKU_DEPTH) // computes how many squares there are
+#define SUDOKU_DEPTH_SQRT 3
+#define SUDOKU_DEPTH      (SUDOKU_DEPTH_SQRT * SUDOKU_DEPTH_SQRT)
+#define SUDOKU_DEPTH_2    (SUDOKU_DEPTH * SUDOKU_DEPTH)
 
 /* bitmask  */
 enum sudoku_bitmask {
@@ -18,8 +19,12 @@ enum sudoku_bitmask {
 	SUDOKU_7 = 0x040,
 	SUDOKU_8 = 0x080,
 	SUDOKU_9 = 0x100,
+	SUDOKU_ALL = 0x01FF,
 };
 
+/* initialises the sudoku board to `SUDOKU_ALL`. (if the tile is empty) */
+void sudoku_init(u16 *board);
+
 /* TODO: write documentation */
 void sudoku_solve_step(u16 *board);