From 5aea129dc9cfb37c1fcb59179a850b802f6a5461 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Wed, 23 Nov 2022 15:50:20 +0000
Subject: [PATCH] Only apply rules to rows

It goes faster this way.
---
 solve.c | 35 +----------------------------------
 1 file changed, 1 insertion(+), 34 deletions(-)

diff --git a/solve.c b/solve.c
index c8ec3b5..cdc7b22 100644
--- a/solve.c
+++ b/solve.c
@@ -83,7 +83,7 @@ static enum apply_res apply_rules(struct sudoku *sud, cellgroup *group)
 int solve(struct sudoku *sud)
 {
 	cellgroup group = { 0 };
-	unsigned r, c, i, j, n;
+	unsigned r, c, n;
 	bool match;
 	enum apply_res res;
 
@@ -105,39 +105,6 @@ int solve(struct sudoku *sud)
 				match = true;
 		}
 
-		/* Apply rules to each column. */
-		for (c = 0; c < NDIGITS; ++c) {
-			for (r = 0; r < NDIGITS; ++r) {
-				group[r].row = r;
-				group[r].col = c;
-				group[r].state = &sud->cells[r][c];
-			}
-
-			res = apply_rules(sud, &group);
-			if (res == ERROR)
-				return -1;
-			else if (res == MATCH)
-				match = true;
-		}
-
-		/* Apply rules to each segment. */
-		for (i = 0; i < NDIGITS; ++i) {
-			for (j = 0; j < NDIGITS; ++j) {
-				r = 3 * (i / 3) + j / 3;
-				c = 3 * (i % 3) + j % 3;
-
-				group[j].row = r;
-				group[j].col = c;
-				group[j].state = &sud->cells[r][c];
-			}
-
-			res = apply_rules(sud, &group);
-			if (res == ERROR)
-				return -1;
-			else if (res == MATCH)
-				match = true;
-		}
-
 		/* Exit if no matches. */
 		if (!match)
 			return n;