Add load() for loading sudokus from text

sud.c

@@ -35,6 +35,18 @@ static void initposs(struct sudoku *sud)
 	}
 }
 
+bool load(struct sudoku *sud, const char *ptr)
+{
+	initposs(sud);
+	for (unsigned i = 0; i < NCELLS; ++i) {
+		if (ptr[i] == '0')
+			continue;
+		if (update(sud, i / NDIGITS, i % NDIGITS, ptr[i] - '1') != OK)
+			return false;
+	}
+	return true;
+}
+
 static void clear(struct sudoku *sud, unsigned r, unsigned c)
 {
 	unsigned tr, tc, val;