Add number of passes to benchmark output

solve.c

@@ -80,14 +80,14 @@ static enum apply_res apply_rules(struct sudoku *sud, cellgroup *group)
 	return matched ? MATCH : NO_MATCH;
 }
 
-bool solve(struct sudoku *sud)
+int solve(struct sudoku *sud)
 {
 	cellgroup group = { 0 };
-	unsigned r, c;
+	unsigned r, c, i, j, n;
 	bool match;
 	enum apply_res res;
 
-	for (unsigned i = 0;; ++i) {
+	for (n = 0;; ++n) {
 		match = false;
 
 		/* Apply rules to each row. */
@@ -100,7 +100,7 @@ bool solve(struct sudoku *sud)
 
 			res = apply_rules(sud, &group);
 			if (res == ERROR)
-				return false;
+				return -1;
 			else if (res == MATCH)
 				match = true;
 		}
@@ -115,7 +115,7 @@ bool solve(struct sudoku *sud)
 
 			res = apply_rules(sud, &group);
 			if (res == ERROR)
-				return false;
+				return -1;
 			else if (res == MATCH)
 				match = true;
 		}
@@ -124,6 +124,6 @@ bool solve(struct sudoku *sud)
 
 		/* Exit if no matches. */
 		if (!match)
-			return true;
+			return n;
 	}
 }