From 120d393f12f7cdc4327803429069350f5c2515ee Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cobrien@witekio.com>
Date: Sun, 9 Mar 2025 11:16:49 +0000
Subject: [PATCH] Fill tiles in search if same in both branches

This gives a ~7% boost in solving ability.
---
 main.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/main.c b/main.c
index 9930d1b..edc3d51 100644
--- a/main.c
+++ b/main.c
@@ -17,8 +17,7 @@
 #define QUEUE_MAX 128
 
 typedef enum {
-	FOUND_MINE,
-	FOUND_SAFE,
+	MADE_INFERENCE,
 	FOUND_NOTHING,
 	FOUND_CONTRADICTION,
 } update_res_t;
@@ -120,7 +119,7 @@ static update_res_t update(state_t *state)
 
 			if (mines + unknowns == state->field[x][y]) {
 				setadj(state->field, x, y, UNKNOWN, MINE);
-				return FOUND_MINE;
+				return MADE_INFERENCE;
 			}
 
 			if (mines == state->field[x][y]) {
@@ -130,7 +129,7 @@ static update_res_t update(state_t *state)
 						enqueue(&state->queue, xi, yi);
 				}
 				setadj(state->field, x, y, UNKNOWN, SAFE);
-				return FOUND_SAFE;
+				return MADE_INFERENCE;
 			}
 		}
 	}
@@ -149,9 +148,9 @@ static update_res_t search_at(state_t *state, int x, int y)
 		if ((res = update(&with_mine)) == FOUND_CONTRADICTION) {
 			state->field[x][y] = SAFE;
 			enqueue(&state->queue, x, y);
-			return FOUND_SAFE;
+			return MADE_INFERENCE;
 		}
-	} while (res != FOUND_NOTHING);
+	} while (res == MADE_INFERENCE);
 
 	state_t with_safe;
 	dup(state, &with_safe);
@@ -159,11 +158,23 @@ static update_res_t search_at(state_t *state, int x, int y)
 	do {
 		if ((res = update(&with_safe)) == FOUND_CONTRADICTION) {
 			state->field[x][y] = MINE;
-			return FOUND_MINE;
+			return MADE_INFERENCE;
 		}
-	} while (res != FOUND_NOTHING);
+	} while (res == MADE_INFERENCE);
 
-	return FOUND_NOTHING;
+	for (int y = 0; y < HEIGHT; ++y) {
+		for (int x = 0; x < WIDTH; ++x) {
+			if (with_mine.field[x][y] == with_safe.field[x][y] &&
+			    state->field[x][y] != with_mine.field[x][y]) {
+				state->field[x][y] = with_mine.field[x][y];
+				if (state->field[x][y] == SAFE)
+					enqueue(&state->queue, x, y);
+				res = MADE_INFERENCE;
+			}
+		}
+	}
+
+	return res;
 }
 
 static update_res_t search(state_t *state)
@@ -208,7 +219,7 @@ static status_t solve(int *probes_out)
 			res = update(&state);
 			if (res == FOUND_NOTHING)
 				res = search(&state);
-		} while (res != FOUND_NOTHING);
+		} while (res == MADE_INFERENCE);
 
 		if (check(state.field) != OK) {
 			printf("Incorrect inference!\n");