diff options
| -rw-r--r-- | bridges.c | 21 |
1 files changed, 18 insertions, 3 deletions
@@ -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", |