fix: not working with full board

src/main.c

@@ -3,8 +3,30 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "sudoku.h"
+
 int main(int argc, char **argv) {
 	(void)argc, (void)argv;
-	printf("%s\n", "Hello, World!");
+	u16 board[SUDOKU_LEN] = {
+		// clang-format off
+		0x010, 0x004, 0x000, 0x000, 0x040, 0x000, 0x000, 0x000, 0x000,
+		0x020, 0x000, 0x000, 0x001, 0x100, 0x010, 0x000, 0x000, 0x000,
+		0x000, 0x100, 0x080, 0x000, 0x000, 0x000, 0x000, 0x020, 0x000,
+		0x080, 0x000, 0x000, 0x000, 0x020, 0x000, 0x000, 0x000, 0x004,
+		0x008, 0x000, 0x000, 0x080, 0x000, 0x004, 0x000, 0x000, 0x001,
+		0x040, 0x000, 0x000, 0x000, 0x002, 0x000, 0x000, 0x000, 0x020,
+		0x000, 0x020, 0x000, 0x000, 0x000, 0x000, 0x002, 0x080, 0x000,
+		0x000, 0x000, 0x000, 0x008, 0x001, 0x100, 0x000, 0x000, 0x010,
+		0x000, 0x000, 0x000, 0x000, 0x080, 0x000, 0x000, 0x040, 0x100,
+		// clang-format on
+	};
+	sudoku_init(board);
+	sudoku_print(board);
+
+	for (int i = 0; i < 2; i++) {
+		sudoku_solve_step(board);
+		sudoku_print(board);
+	}
+
 	return EXIT_SUCCESS;
 }

src/sudoku.c

@@ -9,24 +9,32 @@
 #include "util/intdef.h"
 
 void sudoku_init(u16 *board) {
-	for (uint i = 0; i < SUDOKU_DEPTH_2; i++) {
+	for (uint i = 0; i < SUDOKU_LEN; i++) {
 		board[i] |= SUDOKU_ALL & -!board[i];
 	}
 }
 
-void sudoku_place(u16 *board, u16 val, uint idx) {
-	uint icol = idx % SUDOKU_DEPTH;
-	uint irow = idx - icol;
-	uint ibox = idx - (idx % SUDOKU_DEPTH_SQRT);
-	for (uint i = 0; i < SUDOKU_DEPTH; i++) {
-		board[irow + i] &= ~val;
-		board[icol + (i * SUDOKU_DEPTH)] &= ~val;
-		board[ibox + (i / SUDOKU_DEPTH_SQRT * SUDOKU_DEPTH) + (i % SUDOKU_DEPTH_SQRT)] &= ~val;
+/* removes `val` from `*brd`, if `*brd` is not equal to `val` */
+static inline void setbrdpos(u16 *brd, u16 val) {
+	*brd &= ~(val & -(*brd != val));
+}
+
+void sudoku_place(u16 *brd, u16 val, uint idx) {
+	uint x = idx % SUDOKU_DPT;
+	uint y = idx / SUDOKU_DPT;
+
+	uint irow = idx - x;
+	uint ibox = SUDOKU_DPT * (y % SUDOKU_BOXLEN) + SUDOKU_BOXLEN * (x % SUDOKU_BOXLEN);
+
+	for (uint i = 0; i < SUDOKU_DPT; i++) {
+		setbrdpos(&brd[irow + i], val);
+		setbrdpos(&brd[x + (i * SUDOKU_DPT)], val);
+		setbrdpos(&brd[ibox + (SUDOKU_DPT * (i % SUDOKU_BOXLEN))], val);
 	}
 }
 
 void sudoku_solve_step(u16 *board) {
-	for (uint i = 0; i < SUDOKU_DEPTH_2; i++) {
+	for (uint i = 0; i < SUDOKU_LEN; i++) {
 		switch (board[i]) {
 		case SUDOKU_1:
 		case SUDOKU_2:
@@ -38,14 +46,17 @@ void sudoku_solve_step(u16 *board) {
 		case SUDOKU_8:
 		case SUDOKU_9:
 			sudoku_place(board, board[i], i);
+			// printf("%i,%i\n", i % SUDOKU_DPT, i / SUDOKU_DPT);
 		}
 	}
 }
 
 void sudoku_print(const u16 *board) {
-	for (uint i = 0; i < SUDOKU_DEPTH_2; i++) {
+	printf("+———-———-———-———-———-———-———-———-———+\n");
+	for (uint i = 0; i < SUDOKU_LEN; i++) {
 		char tile;
 		switch (board[i]) {
+		// case 0:        tile = 'x'; break;
 		case SUDOKU_1: tile = '1'; break;
 		case SUDOKU_2: tile = '2'; break;
 		case SUDOKU_3: tile = '3'; break;
@@ -58,7 +69,9 @@ void sudoku_print(const u16 *board) {
 		default:       tile = ' '; break;
 		};
 
-		printf("|%c ", tile);
+		printf("| %c ", tile);
+		// printf("|%3X", board[i]);
 		if (i % 9 == 8) printf("|\n");
 	}
+	printf("+———-———-———-———-———-———-———-———-———+\n");
 }

src/sudoku.h

@@ -4,9 +4,9 @@
 
 #include "util/intdef.h"
 
-#define SUDOKU_DEPTH_SQRT 3
-#define SUDOKU_DEPTH      (SUDOKU_DEPTH_SQRT * SUDOKU_DEPTH_SQRT)
-#define SUDOKU_DEPTH_2    (SUDOKU_DEPTH * SUDOKU_DEPTH)
+#define SUDOKU_BOXLEN     3
+#define SUDOKU_DPT        9
+#define SUDOKU_LEN        (SUDOKU_DPT * SUDOKU_DPT)
 
 /* bitmask  */
 enum sudoku_bitmask {