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Filling: switch to using dsf_minimal in minimize_clue_set.

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Turns out that was another case where we were assuming the canonical
dsf element was also the minimal one, because we process the clues in
order and expect to start a linked list at the canonical element of
each region and then add the rest of the cells to the existing one.

Easily fixed by using the minimal element again.
This commit is contained in:
Simon Tatham
2023-04-21 09:26:14 +01:00
parent ce203c12ef
commit 20606f0fea
1 changed files with 4 additions and 4 deletions
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8
filling.c
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@ -1135,7 +1135,7 @@ static DSF *make_dsf(DSF *dsf, int *board, const int w, const int h) {
int i; int i;
if (!dsf) if (!dsf)
dsf = dsf_new(w * h); dsf = dsf_new_min(w * h);
else else
dsf_reinit(dsf); dsf_reinit(dsf);
@ -1174,14 +1174,14 @@ static void minimize_clue_set(int *board, int w, int h, random_state *rs)
dsf = make_dsf(NULL, board, w, h); dsf = make_dsf(NULL, board, w, h);
next = snewn(sz, int); next = snewn(sz, int);
for (i = 0; i < sz; ++i) { for (i = 0; i < sz; ++i) {
int j = dsf_canonify(dsf, i); int j = dsf_minimal(dsf, i);
if (i == j) { if (i == j) {
/* First cell of a region; set next[i] = -1 to indicate /* First cell of a region; set next[i] = -1 to indicate
* end-of-list. */ * end-of-list. */
next[i] = -1; next[i] = -1;
} else { } else {
/* Add this cell to a region which already has a /* Add this cell to a region which already has a
* linked-list head, by pointing the canonical element j * linked-list head, by pointing the minimal element j
* at this one, and pointing this one in turn at wherever * at this one, and pointing this one in turn at wherever
* j previously pointed. (This should end up with the * j previously pointed. (This should end up with the
* elements linked in the order 1,n,n-1,n-2,...,2, which * elements linked in the order 1,n,n-1,n-2,...,2, which
@ -1209,7 +1209,7 @@ static void minimize_clue_set(int *board, int w, int h, random_state *rs)
* if we can. * if we can.
*/ */
for (i = 0; i < sz; ++i) { for (i = 0; i < sz; ++i) {
int j = dsf_canonify(dsf, shuf[i]); int j = dsf_minimal(dsf, shuf[i]);
if (next[j] != -2) { if (next[j] != -2) {
int tmp = board[j]; int tmp = board[j];
int k; int k;