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Improve connectedness-error highlighting in Range.

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The previous approach of scanning the grid by depth-first search was
fine for deciding whether it was connected, but not so good for
pointing out where the mistake was in the grid. Replaced that code
with a dsf-based version, which identifies all connected components so
that an easy followup pass can highlight all but the largest as
erroneous.

[originally from svn r10223]
This commit is contained in:
Simon Tatham
2014-09-09 14:20:10 +00:00
parent ff8a9fbc54
commit ac6fd11dda
2 changed files with 45 additions and 6 deletions
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43
range.c
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@ -1364,6 +1364,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
static int find_errors(const game_state *state, int *report)
{
int const w = state->params.w, h = state->params.h, n = w * h;
int *dsf;
int r, c, i;
@ -1415,14 +1416,50 @@ static int find_errors(const game_state *state, int *report)
}
}
for (i = 0; i < n; ++i) if (dup->grid[i] != BLACK) dup->grid[i] = WHITE;
if (nblack + dfs_count_white(dup, any_white_cell) < n) {
/*
* Check that all the white cells form a single connected component.
*/
dsf = snew_dsf(n);
for (r = 0; r < h-1; ++r)
for (c = 0; c < w; ++c)
if (state->grid[r*w+c] != BLACK &&
state->grid[(r+1)*w+c] != BLACK)
dsf_merge(dsf, r*w+c, (r+1)*w+c);
for (r = 0; r < h; ++r)
for (c = 0; c < w-1; ++c)
if (state->grid[r*w+c] != BLACK &&
state->grid[r*w+(c+1)] != BLACK)
dsf_merge(dsf, r*w+c, r*w+(c+1));
if (nblack + dsf_size(dsf, any_white_cell) < n) {
int biggest, canonical;
if (!report) {
printf("dfs fail at %d\n", any_white_cell);
goto found_error;
}
for (i = 0; i < n; ++i) if (state->grid[i] != BLACK) report[i] = TRUE;
/*
* Report this error by choosing one component to be the
* canonical one (we pick the largest, arbitrarily
* tie-breaking towards lower array indices) and highlighting
* as an error any square in a different component.
*/
canonical = -1;
biggest = 0;
for (i = 0; i < n; ++i)
if (state->grid[i] != BLACK) {
int size = dsf_size(dsf, i);
if (size > biggest) {
biggest = size;
canonical = dsf_canonify(dsf, i);
}
}
for (i = 0; i < n; ++i)
if (state->grid[i] != BLACK && dsf_canonify(dsf, i) != canonical)
report[i] = TRUE;
}
sfree(dsf);
free_game(dup);
return FALSE; /* if report != NULL, this is ignored */