X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/puzzles/blobdiff_plain/9a6d429a8372cc31fb1aa7de8e5f079a47ecf148..f04d88ba2c57c09a2e2598558ff1a42a7d86cfde:/bridges.c

diff --git a/bridges.c b/bridges.c
index 64501ef..4219df4 100644
--- a/bridges.c
+++ b/bridges.c
@@ -542,9 +542,24 @@ static int island_impossible(struct island *is, int strict)
         assert(is_orth);
 
         ifree = is_orth->count - island_countbridges(is_orth);
-        if (ifree > 0)
-            nsurrspc += min(ifree, MAXIMUM(is->state, dx,
-                                           is->adj.points[i].x, is->adj.points[i].y));
+        if (ifree > 0) {
+	    /*
+	     * ifree is the number of bridges unfilled in the other
+	     * island, which is clearly an upper bound on the number
+	     * of extra bridges this island may run to it.
+	     *
+	     * Another upper bound is the number of bridges unfilled
+	     * on the specific line between here and there. We must
+	     * take the minimum of both.
+	     */
+	    int bmax = MAXIMUM(is->state, dx,
+			       is->adj.points[i].x, is->adj.points[i].y);
+	    int bcurr = GRIDCOUNT(is->state,
+				  is->adj.points[i].x, is->adj.points[i].y,
+				  dx ? G_LINEH : G_LINEV);
+	    assert(bcurr <= bmax);
+            nsurrspc += min(ifree, bmax - bcurr);
+	}
     }
     if (nsurrspc < nspc) {
         debug(("island at (%d,%d) impossible: surr. islands %d spc, need %d.\n",
@@ -2479,7 +2494,7 @@ static void dsf_debug_draw(drawing *dr,
 #ifdef DRAW_DSF
     int ts = TILE_SIZE/2;
     int ox = COORD(x) + ts/2, oy = COORD(y) + ts/2;
-    char str[10];
+    char str[32];
 
     sprintf(str, "%d", dsf_canonify(state->solver->dsf, DINDEX(x,y)));
     draw_text(dr, ox, oy, FONT_VARIABLE, ts,
@@ -2556,7 +2571,7 @@ static void island_redraw(drawing *dr,
     int col = (v & G_ISSEL) ? COL_SELECTED : tcol;
     int bg = (v & G_CURSOR) ? COL_CURSOR :
         (v & G_MARK) ? COL_MARK : COL_BACKGROUND;
-    char str[10];
+    char str[32];
 
 #ifdef DRAW_GRID
     draw_rect_outline(dr, COORD(is->x), COORD(is->y),
@@ -2759,7 +2774,7 @@ static void game_print(drawing *dr, game_state *state, int ts)
 
     /* Islands */
     for (i = 0; i < state->n_islands; i++) {
-        char str[10];
+        char str[32];
         struct island *is = &state->islands[i];
         grid = GRID(state, is->x, is->y);
         cx = COORD(is->x) + ts/2;