2 * solo.c: the number-placing puzzle most popularly known as `Sudoku'.
6 * - it might still be nice to do some prioritisation on the
7 * removal of numbers from the grid
8 * + one possibility is to try to minimise the maximum number
9 * of filled squares in any block, which in particular ought
10 * to enforce never leaving a completely filled block in the
11 * puzzle as presented.
13 * - alternative interface modes
14 * + sudoku.com's Windows program has a palette of possible
15 * entries; you select a palette entry first and then click
16 * on the square you want it to go in, thus enabling
17 * mouse-only play. Useful for PDAs! I don't think it's
18 * actually incompatible with the current highlight-then-type
19 * approach: you _either_ highlight a palette entry and then
20 * click, _or_ you highlight a square and then type. At most
21 * one thing is ever highlighted at a time, so there's no way
23 * + `pencil marks' might be useful for more subtle forms of
24 * deduction, now we can create puzzles that require them.
28 * Solo puzzles need to be square overall (since each row and each
29 * column must contain one of every digit), but they need not be
30 * subdivided the same way internally. I am going to adopt a
31 * convention whereby I _always_ refer to `r' as the number of rows
32 * of _big_ divisions, and `c' as the number of columns of _big_
33 * divisions. Thus, a 2c by 3r puzzle looks something like this:
37 * ------+------ (Of course, you can't subdivide it the other way
38 * 1 4 5 | 6 3 2 or you'll get clashes; observe that the 4 in the
39 * 3 2 6 | 4 1 5 top left would conflict with the 4 in the second
40 * ------+------ box down on the left-hand side.)
44 * The need for a strong naming convention should now be clear:
45 * each small box is two rows of digits by three columns, while the
46 * overall puzzle has three rows of small boxes by two columns. So
47 * I will (hopefully) consistently use `r' to denote the number of
48 * rows _of small boxes_ (here 3), which is also the number of
49 * columns of digits in each small box; and `c' vice versa (here
52 * I'm also going to choose arbitrarily to list c first wherever
53 * possible: the above is a 2x3 puzzle, not a 3x2 one.
63 #ifdef STANDALONE_SOLVER
65 int solver_show_working;
70 #define max(x,y) ((x)>(y)?(x):(y))
73 * To save space, I store digits internally as unsigned char. This
74 * imposes a hard limit of 255 on the order of the puzzle. Since
75 * even a 5x5 takes unacceptably long to generate, I don't see this
76 * as a serious limitation unless something _really_ impressive
77 * happens in computing technology; but here's a typedef anyway for
78 * general good practice.
80 typedef unsigned char digit;
86 #define FLASH_TIME 0.4F
88 enum { SYMM_NONE, SYMM_ROT2, SYMM_ROT4, SYMM_REF4 };
90 enum { DIFF_BLOCK, DIFF_SIMPLE, DIFF_INTERSECT,
91 DIFF_SET, DIFF_RECURSIVE, DIFF_AMBIGUOUS, DIFF_IMPOSSIBLE };
103 int c, r, symm, diff;
109 unsigned char *immutable; /* marks which digits are clues */
110 int completed, cheated;
113 static game_params *default_params(void)
115 game_params *ret = snew(game_params);
118 ret->symm = SYMM_ROT2; /* a plausible default */
119 ret->diff = DIFF_SIMPLE; /* so is this */
124 static void free_params(game_params *params)
129 static game_params *dup_params(game_params *params)
131 game_params *ret = snew(game_params);
132 *ret = *params; /* structure copy */
136 static int game_fetch_preset(int i, char **name, game_params **params)
142 { "2x2 Trivial", { 2, 2, SYMM_ROT2, DIFF_BLOCK } },
143 { "2x3 Basic", { 2, 3, SYMM_ROT2, DIFF_SIMPLE } },
144 { "3x3 Basic", { 3, 3, SYMM_ROT2, DIFF_SIMPLE } },
145 { "3x3 Intermediate", { 3, 3, SYMM_ROT2, DIFF_INTERSECT } },
146 { "3x3 Advanced", { 3, 3, SYMM_ROT2, DIFF_SET } },
147 { "3x3 Unreasonable", { 3, 3, SYMM_ROT2, DIFF_RECURSIVE } },
148 { "3x4 Basic", { 3, 4, SYMM_ROT2, DIFF_SIMPLE } },
149 { "4x4 Basic", { 4, 4, SYMM_ROT2, DIFF_SIMPLE } },
152 if (i < 0 || i >= lenof(presets))
155 *name = dupstr(presets[i].title);
156 *params = dup_params(&presets[i].params);
161 static game_params *decode_params(char const *string)
163 game_params *ret = default_params();
165 ret->c = ret->r = atoi(string);
166 ret->symm = SYMM_ROT2;
167 while (*string && isdigit((unsigned char)*string)) string++;
168 if (*string == 'x') {
170 ret->r = atoi(string);
171 while (*string && isdigit((unsigned char)*string)) string++;
174 if (*string == 'r' || *string == 'm' || *string == 'a') {
178 while (*string && isdigit((unsigned char)*string)) string++;
179 if (sc == 'm' && sn == 4)
180 ret->symm = SYMM_REF4;
181 if (sc == 'r' && sn == 4)
182 ret->symm = SYMM_ROT4;
183 if (sc == 'r' && sn == 2)
184 ret->symm = SYMM_ROT2;
186 ret->symm = SYMM_NONE;
187 } else if (*string == 'd') {
189 if (*string == 't') /* trivial */
190 string++, ret->diff = DIFF_BLOCK;
191 else if (*string == 'b') /* basic */
192 string++, ret->diff = DIFF_SIMPLE;
193 else if (*string == 'i') /* intermediate */
194 string++, ret->diff = DIFF_INTERSECT;
195 else if (*string == 'a') /* advanced */
196 string++, ret->diff = DIFF_SET;
197 else if (*string == 'u') /* unreasonable */
198 string++, ret->diff = DIFF_RECURSIVE;
200 string++; /* eat unknown character */
206 static char *encode_params(game_params *params)
211 * Symmetry is a game generation preference and hence is left
212 * out of the encoding. Users can add it back in as they see
215 sprintf(str, "%dx%d", params->c, params->r);
219 static config_item *game_configure(game_params *params)
224 ret = snewn(5, config_item);
226 ret[0].name = "Columns of sub-blocks";
227 ret[0].type = C_STRING;
228 sprintf(buf, "%d", params->c);
229 ret[0].sval = dupstr(buf);
232 ret[1].name = "Rows of sub-blocks";
233 ret[1].type = C_STRING;
234 sprintf(buf, "%d", params->r);
235 ret[1].sval = dupstr(buf);
238 ret[2].name = "Symmetry";
239 ret[2].type = C_CHOICES;
240 ret[2].sval = ":None:2-way rotation:4-way rotation:4-way mirror";
241 ret[2].ival = params->symm;
243 ret[3].name = "Difficulty";
244 ret[3].type = C_CHOICES;
245 ret[3].sval = ":Trivial:Basic:Intermediate:Advanced:Unreasonable";
246 ret[3].ival = params->diff;
256 static game_params *custom_params(config_item *cfg)
258 game_params *ret = snew(game_params);
260 ret->c = atoi(cfg[0].sval);
261 ret->r = atoi(cfg[1].sval);
262 ret->symm = cfg[2].ival;
263 ret->diff = cfg[3].ival;
268 static char *validate_params(game_params *params)
270 if (params->c < 2 || params->r < 2)
271 return "Both dimensions must be at least 2";
272 if (params->c > ORDER_MAX || params->r > ORDER_MAX)
273 return "Dimensions greater than "STR(ORDER_MAX)" are not supported";
277 /* ----------------------------------------------------------------------
278 * Full recursive Solo solver.
280 * The algorithm for this solver is shamelessly copied from a
281 * Python solver written by Andrew Wilkinson (which is GPLed, but
282 * I've reused only ideas and no code). It mostly just does the
283 * obvious recursive thing: pick an empty square, put one of the
284 * possible digits in it, recurse until all squares are filled,
285 * backtrack and change some choices if necessary.
287 * The clever bit is that every time it chooses which square to
288 * fill in next, it does so by counting the number of _possible_
289 * numbers that can go in each square, and it prioritises so that
290 * it picks a square with the _lowest_ number of possibilities. The
291 * idea is that filling in lots of the obvious bits (particularly
292 * any squares with only one possibility) will cut down on the list
293 * of possibilities for other squares and hence reduce the enormous
294 * search space as much as possible as early as possible.
296 * In practice the algorithm appeared to work very well; run on
297 * sample problems from the Times it completed in well under a
298 * second on my G5 even when written in Python, and given an empty
299 * grid (so that in principle it would enumerate _all_ solved
300 * grids!) it found the first valid solution just as quickly. So
301 * with a bit more randomisation I see no reason not to use this as
306 * Internal data structure used in solver to keep track of
309 struct rsolve_coord { int x, y, r; };
310 struct rsolve_usage {
311 int c, r, cr; /* cr == c*r */
312 /* grid is a copy of the input grid, modified as we go along */
314 /* row[y*cr+n-1] TRUE if digit n has been placed in row y */
316 /* col[x*cr+n-1] TRUE if digit n has been placed in row x */
318 /* blk[(y*c+x)*cr+n-1] TRUE if digit n has been placed in block (x,y) */
320 /* This lists all the empty spaces remaining in the grid. */
321 struct rsolve_coord *spaces;
323 /* If we need randomisation in the solve, this is our random state. */
325 /* Number of solutions so far found, and maximum number we care about. */
330 * The real recursive step in the solving function.
332 static void rsolve_real(struct rsolve_usage *usage, digit *grid)
334 int c = usage->c, r = usage->r, cr = usage->cr;
335 int i, j, n, sx, sy, bestm, bestr;
339 * Firstly, check for completion! If there are no spaces left
340 * in the grid, we have a solution.
342 if (usage->nspaces == 0) {
345 * This is our first solution, so fill in the output grid.
347 memcpy(grid, usage->grid, cr * cr);
354 * Otherwise, there must be at least one space. Find the most
355 * constrained space, using the `r' field as a tie-breaker.
357 bestm = cr+1; /* so that any space will beat it */
360 for (j = 0; j < usage->nspaces; j++) {
361 int x = usage->spaces[j].x, y = usage->spaces[j].y;
365 * Find the number of digits that could go in this space.
368 for (n = 0; n < cr; n++)
369 if (!usage->row[y*cr+n] && !usage->col[x*cr+n] &&
370 !usage->blk[((y/c)*c+(x/r))*cr+n])
373 if (m < bestm || (m == bestm && usage->spaces[j].r < bestr)) {
375 bestr = usage->spaces[j].r;
383 * Swap that square into the final place in the spaces array,
384 * so that decrementing nspaces will remove it from the list.
386 if (i != usage->nspaces-1) {
387 struct rsolve_coord t;
388 t = usage->spaces[usage->nspaces-1];
389 usage->spaces[usage->nspaces-1] = usage->spaces[i];
390 usage->spaces[i] = t;
394 * Now we've decided which square to start our recursion at,
395 * simply go through all possible values, shuffling them
396 * randomly first if necessary.
398 digits = snewn(bestm, int);
400 for (n = 0; n < cr; n++)
401 if (!usage->row[sy*cr+n] && !usage->col[sx*cr+n] &&
402 !usage->blk[((sy/c)*c+(sx/r))*cr+n]) {
408 for (i = j; i > 1; i--) {
409 int p = random_upto(usage->rs, i);
412 digits[p] = digits[i-1];
418 /* And finally, go through the digit list and actually recurse. */
419 for (i = 0; i < j; i++) {
422 /* Update the usage structure to reflect the placing of this digit. */
423 usage->row[sy*cr+n-1] = usage->col[sx*cr+n-1] =
424 usage->blk[((sy/c)*c+(sx/r))*cr+n-1] = TRUE;
425 usage->grid[sy*cr+sx] = n;
428 /* Call the solver recursively. */
429 rsolve_real(usage, grid);
432 * If we have seen as many solutions as we need, terminate
433 * all processing immediately.
435 if (usage->solns >= usage->maxsolns)
438 /* Revert the usage structure. */
439 usage->row[sy*cr+n-1] = usage->col[sx*cr+n-1] =
440 usage->blk[((sy/c)*c+(sx/r))*cr+n-1] = FALSE;
441 usage->grid[sy*cr+sx] = 0;
449 * Entry point to solver. You give it dimensions and a starting
450 * grid, which is simply an array of N^4 digits. In that array, 0
451 * means an empty square, and 1..N mean a clue square.
453 * Return value is the number of solutions found; searching will
454 * stop after the provided `max'. (Thus, you can pass max==1 to
455 * indicate that you only care about finding _one_ solution, or
456 * max==2 to indicate that you want to know the difference between
457 * a unique and non-unique solution.) The input parameter `grid' is
458 * also filled in with the _first_ (or only) solution found by the
461 static int rsolve(int c, int r, digit *grid, random_state *rs, int max)
463 struct rsolve_usage *usage;
468 * Create an rsolve_usage structure.
470 usage = snew(struct rsolve_usage);
476 usage->grid = snewn(cr * cr, digit);
477 memcpy(usage->grid, grid, cr * cr);
479 usage->row = snewn(cr * cr, unsigned char);
480 usage->col = snewn(cr * cr, unsigned char);
481 usage->blk = snewn(cr * cr, unsigned char);
482 memset(usage->row, FALSE, cr * cr);
483 memset(usage->col, FALSE, cr * cr);
484 memset(usage->blk, FALSE, cr * cr);
486 usage->spaces = snewn(cr * cr, struct rsolve_coord);
490 usage->maxsolns = max;
495 * Now fill it in with data from the input grid.
497 for (y = 0; y < cr; y++) {
498 for (x = 0; x < cr; x++) {
499 int v = grid[y*cr+x];
501 usage->spaces[usage->nspaces].x = x;
502 usage->spaces[usage->nspaces].y = y;
504 usage->spaces[usage->nspaces].r = random_bits(rs, 31);
506 usage->spaces[usage->nspaces].r = usage->nspaces;
509 usage->row[y*cr+v-1] = TRUE;
510 usage->col[x*cr+v-1] = TRUE;
511 usage->blk[((y/c)*c+(x/r))*cr+v-1] = TRUE;
517 * Run the real recursive solving function.
519 rsolve_real(usage, grid);
523 * Clean up the usage structure now we have our answer.
525 sfree(usage->spaces);
538 /* ----------------------------------------------------------------------
539 * End of recursive solver code.
542 /* ----------------------------------------------------------------------
543 * Less capable non-recursive solver. This one is used to check
544 * solubility of a grid as we gradually remove numbers from it: by
545 * verifying a grid using this solver we can ensure it isn't _too_
546 * hard (e.g. does not actually require guessing and backtracking).
548 * It supports a variety of specific modes of reasoning. By
549 * enabling or disabling subsets of these modes we can arrange a
550 * range of difficulty levels.
554 * Modes of reasoning currently supported:
556 * - Positional elimination: a number must go in a particular
557 * square because all the other empty squares in a given
558 * row/col/blk are ruled out.
560 * - Numeric elimination: a square must have a particular number
561 * in because all the other numbers that could go in it are
564 * - Intersectional analysis: given two domains which overlap
565 * (hence one must be a block, and the other can be a row or
566 * col), if the possible locations for a particular number in
567 * one of the domains can be narrowed down to the overlap, then
568 * that number can be ruled out everywhere but the overlap in
569 * the other domain too.
571 * - Set elimination: if there is a subset of the empty squares
572 * within a domain such that the union of the possible numbers
573 * in that subset has the same size as the subset itself, then
574 * those numbers can be ruled out everywhere else in the domain.
575 * (For example, if there are five empty squares and the
576 * possible numbers in each are 12, 23, 13, 134 and 1345, then
577 * the first three empty squares form such a subset: the numbers
578 * 1, 2 and 3 _must_ be in those three squares in some
579 * permutation, and hence we can deduce none of them can be in
580 * the fourth or fifth squares.)
581 * + You can also see this the other way round, concentrating
582 * on numbers rather than squares: if there is a subset of
583 * the unplaced numbers within a domain such that the union
584 * of all their possible positions has the same size as the
585 * subset itself, then all other numbers can be ruled out for
586 * those positions. However, it turns out that this is
587 * exactly equivalent to the first formulation at all times:
588 * there is a 1-1 correspondence between suitable subsets of
589 * the unplaced numbers and suitable subsets of the unfilled
590 * places, found by taking the _complement_ of the union of
591 * the numbers' possible positions (or the spaces' possible
596 * Within this solver, I'm going to transform all y-coordinates by
597 * inverting the significance of the block number and the position
598 * within the block. That is, we will start with the top row of
599 * each block in order, then the second row of each block in order,
602 * This transformation has the enormous advantage that it means
603 * every row, column _and_ block is described by an arithmetic
604 * progression of coordinates within the cubic array, so that I can
605 * use the same very simple function to do blockwise, row-wise and
606 * column-wise elimination.
608 #define YTRANS(y) (((y)%c)*r+(y)/c)
609 #define YUNTRANS(y) (((y)%r)*c+(y)/r)
611 struct nsolve_usage {
614 * We set up a cubic array, indexed by x, y and digit; each
615 * element of this array is TRUE or FALSE according to whether
616 * or not that digit _could_ in principle go in that position.
618 * The way to index this array is cube[(x*cr+y)*cr+n-1].
619 * y-coordinates in here are transformed.
623 * This is the grid in which we write down our final
624 * deductions. y-coordinates in here are _not_ transformed.
628 * Now we keep track, at a slightly higher level, of what we
629 * have yet to work out, to prevent doing the same deduction
632 /* row[y*cr+n-1] TRUE if digit n has been placed in row y */
634 /* col[x*cr+n-1] TRUE if digit n has been placed in row x */
636 /* blk[(y*c+x)*cr+n-1] TRUE if digit n has been placed in block (x,y) */
639 #define cubepos(x,y,n) (((x)*usage->cr+(y))*usage->cr+(n)-1)
640 #define cube(x,y,n) (usage->cube[cubepos(x,y,n)])
643 * Function called when we are certain that a particular square has
644 * a particular number in it. The y-coordinate passed in here is
647 static void nsolve_place(struct nsolve_usage *usage, int x, int y, int n)
649 int c = usage->c, r = usage->r, cr = usage->cr;
655 * Rule out all other numbers in this square.
657 for (i = 1; i <= cr; i++)
662 * Rule out this number in all other positions in the row.
664 for (i = 0; i < cr; i++)
669 * Rule out this number in all other positions in the column.
671 for (i = 0; i < cr; i++)
676 * Rule out this number in all other positions in the block.
680 for (i = 0; i < r; i++)
681 for (j = 0; j < c; j++)
682 if (bx+i != x || by+j*r != y)
683 cube(bx+i,by+j*r,n) = FALSE;
686 * Enter the number in the result grid.
688 usage->grid[YUNTRANS(y)*cr+x] = n;
691 * Cross out this number from the list of numbers left to place
692 * in its row, its column and its block.
694 usage->row[y*cr+n-1] = usage->col[x*cr+n-1] =
695 usage->blk[((y%r)*c+(x/r))*cr+n-1] = TRUE;
698 static int nsolve_elim(struct nsolve_usage *usage, int start, int step
699 #ifdef STANDALONE_SOLVER
704 int c = usage->c, r = usage->r, cr = c*r;
708 * Count the number of set bits within this section of the
713 for (i = 0; i < cr; i++)
714 if (usage->cube[start+i*step]) {
728 if (!usage->grid[YUNTRANS(y)*cr+x]) {
729 #ifdef STANDALONE_SOLVER
730 if (solver_show_working) {
735 printf(":\n placing %d at (%d,%d)\n",
736 n, 1+x, 1+YUNTRANS(y));
739 nsolve_place(usage, x, y, n);
747 static int nsolve_intersect(struct nsolve_usage *usage,
748 int start1, int step1, int start2, int step2
749 #ifdef STANDALONE_SOLVER
754 int c = usage->c, r = usage->r, cr = c*r;
758 * Loop over the first domain and see if there's any set bit
759 * not also in the second.
761 for (i = 0; i < cr; i++) {
762 int p = start1+i*step1;
763 if (usage->cube[p] &&
764 !(p >= start2 && p < start2+cr*step2 &&
765 (p - start2) % step2 == 0))
766 return FALSE; /* there is, so we can't deduce */
770 * We have determined that all set bits in the first domain are
771 * within its overlap with the second. So loop over the second
772 * domain and remove all set bits that aren't also in that
773 * overlap; return TRUE iff we actually _did_ anything.
776 for (i = 0; i < cr; i++) {
777 int p = start2+i*step2;
778 if (usage->cube[p] &&
779 !(p >= start1 && p < start1+cr*step1 && (p - start1) % step1 == 0))
781 #ifdef STANDALONE_SOLVER
782 if (solver_show_working) {
798 printf(" ruling out %d at (%d,%d)\n",
799 pn, 1+px, 1+YUNTRANS(py));
802 ret = TRUE; /* we did something */
810 static int nsolve_set(struct nsolve_usage *usage,
811 int start, int step1, int step2
812 #ifdef STANDALONE_SOLVER
817 int c = usage->c, r = usage->r, cr = c*r;
819 unsigned char *grid = snewn(cr*cr, unsigned char);
820 unsigned char *rowidx = snewn(cr, unsigned char);
821 unsigned char *colidx = snewn(cr, unsigned char);
822 unsigned char *set = snewn(cr, unsigned char);
825 * We are passed a cr-by-cr matrix of booleans. Our first job
826 * is to winnow it by finding any definite placements - i.e.
827 * any row with a solitary 1 - and discarding that row and the
828 * column containing the 1.
830 memset(rowidx, TRUE, cr);
831 memset(colidx, TRUE, cr);
832 for (i = 0; i < cr; i++) {
833 int count = 0, first = -1;
834 for (j = 0; j < cr; j++)
835 if (usage->cube[start+i*step1+j*step2])
839 * This condition actually marks a completely insoluble
840 * (i.e. internally inconsistent) puzzle. We return and
841 * report no progress made.
846 rowidx[i] = colidx[first] = FALSE;
850 * Convert each of rowidx/colidx from a list of 0s and 1s to a
851 * list of the indices of the 1s.
853 for (i = j = 0; i < cr; i++)
857 for (i = j = 0; i < cr; i++)
863 * And create the smaller matrix.
865 for (i = 0; i < n; i++)
866 for (j = 0; j < n; j++)
867 grid[i*cr+j] = usage->cube[start+rowidx[i]*step1+colidx[j]*step2];
870 * Having done that, we now have a matrix in which every row
871 * has at least two 1s in. Now we search to see if we can find
872 * a rectangle of zeroes (in the set-theoretic sense of
873 * `rectangle', i.e. a subset of rows crossed with a subset of
874 * columns) whose width and height add up to n.
881 * We have a candidate set. If its size is <=1 or >=n-1
882 * then we move on immediately.
884 if (count > 1 && count < n-1) {
886 * The number of rows we need is n-count. See if we can
887 * find that many rows which each have a zero in all
888 * the positions listed in `set'.
891 for (i = 0; i < n; i++) {
893 for (j = 0; j < n; j++)
894 if (set[j] && grid[i*cr+j]) {
903 * We expect never to be able to get _more_ than
904 * n-count suitable rows: this would imply that (for
905 * example) there are four numbers which between them
906 * have at most three possible positions, and hence it
907 * indicates a faulty deduction before this point or
910 assert(rows <= n - count);
911 if (rows >= n - count) {
912 int progress = FALSE;
915 * We've got one! Now, for each row which _doesn't_
916 * satisfy the criterion, eliminate all its set
917 * bits in the positions _not_ listed in `set'.
918 * Return TRUE (meaning progress has been made) if
919 * we successfully eliminated anything at all.
921 * This involves referring back through
922 * rowidx/colidx in order to work out which actual
923 * positions in the cube to meddle with.
925 for (i = 0; i < n; i++) {
927 for (j = 0; j < n; j++)
928 if (set[j] && grid[i*cr+j]) {
933 for (j = 0; j < n; j++)
934 if (!set[j] && grid[i*cr+j]) {
935 int fpos = (start+rowidx[i]*step1+
937 #ifdef STANDALONE_SOLVER
938 if (solver_show_working) {
954 printf(" ruling out %d at (%d,%d)\n",
955 pn, 1+px, 1+YUNTRANS(py));
959 usage->cube[fpos] = FALSE;
975 * Binary increment: change the rightmost 0 to a 1, and
976 * change all 1s to the right of it to 0s.
979 while (i > 0 && set[i-1])
980 set[--i] = 0, count--;
982 set[--i] = 1, count++;
995 static int nsolve(int c, int r, digit *grid)
997 struct nsolve_usage *usage;
1000 int diff = DIFF_BLOCK;
1003 * Set up a usage structure as a clean slate (everything
1006 usage = snew(struct nsolve_usage);
1010 usage->cube = snewn(cr*cr*cr, unsigned char);
1011 usage->grid = grid; /* write straight back to the input */
1012 memset(usage->cube, TRUE, cr*cr*cr);
1014 usage->row = snewn(cr * cr, unsigned char);
1015 usage->col = snewn(cr * cr, unsigned char);
1016 usage->blk = snewn(cr * cr, unsigned char);
1017 memset(usage->row, FALSE, cr * cr);
1018 memset(usage->col, FALSE, cr * cr);
1019 memset(usage->blk, FALSE, cr * cr);
1022 * Place all the clue numbers we are given.
1024 for (x = 0; x < cr; x++)
1025 for (y = 0; y < cr; y++)
1027 nsolve_place(usage, x, YTRANS(y), grid[y*cr+x]);
1030 * Now loop over the grid repeatedly trying all permitted modes
1031 * of reasoning. The loop terminates if we complete an
1032 * iteration without making any progress; we then return
1033 * failure or success depending on whether the grid is full or
1038 * I'd like to write `continue;' inside each of the
1039 * following loops, so that the solver returns here after
1040 * making some progress. However, I can't specify that I
1041 * want to continue an outer loop rather than the innermost
1042 * one, so I'm apologetically resorting to a goto.
1047 * Blockwise positional elimination.
1049 for (x = 0; x < cr; x += r)
1050 for (y = 0; y < r; y++)
1051 for (n = 1; n <= cr; n++)
1052 if (!usage->blk[(y*c+(x/r))*cr+n-1] &&
1053 nsolve_elim(usage, cubepos(x,y,n), r*cr
1054 #ifdef STANDALONE_SOLVER
1055 , "positional elimination,"
1056 " block (%d,%d)", 1+x/r, 1+y
1059 diff = max(diff, DIFF_BLOCK);
1064 * Row-wise positional elimination.
1066 for (y = 0; y < cr; y++)
1067 for (n = 1; n <= cr; n++)
1068 if (!usage->row[y*cr+n-1] &&
1069 nsolve_elim(usage, cubepos(0,y,n), cr*cr
1070 #ifdef STANDALONE_SOLVER
1071 , "positional elimination,"
1072 " row %d", 1+YUNTRANS(y)
1075 diff = max(diff, DIFF_SIMPLE);
1079 * Column-wise positional elimination.
1081 for (x = 0; x < cr; x++)
1082 for (n = 1; n <= cr; n++)
1083 if (!usage->col[x*cr+n-1] &&
1084 nsolve_elim(usage, cubepos(x,0,n), cr
1085 #ifdef STANDALONE_SOLVER
1086 , "positional elimination," " column %d", 1+x
1089 diff = max(diff, DIFF_SIMPLE);
1094 * Numeric elimination.
1096 for (x = 0; x < cr; x++)
1097 for (y = 0; y < cr; y++)
1098 if (!usage->grid[YUNTRANS(y)*cr+x] &&
1099 nsolve_elim(usage, cubepos(x,y,1), 1
1100 #ifdef STANDALONE_SOLVER
1101 , "numeric elimination at (%d,%d)", 1+x,
1105 diff = max(diff, DIFF_SIMPLE);
1110 * Intersectional analysis, rows vs blocks.
1112 for (y = 0; y < cr; y++)
1113 for (x = 0; x < cr; x += r)
1114 for (n = 1; n <= cr; n++)
1115 if (!usage->row[y*cr+n-1] &&
1116 !usage->blk[((y%r)*c+(x/r))*cr+n-1] &&
1117 (nsolve_intersect(usage, cubepos(0,y,n), cr*cr,
1118 cubepos(x,y%r,n), r*cr
1119 #ifdef STANDALONE_SOLVER
1120 , "intersectional analysis,"
1121 " row %d vs block (%d,%d)",
1122 1+YUNTRANS(y), 1+x/r, 1+y%r
1125 nsolve_intersect(usage, cubepos(x,y%r,n), r*cr,
1126 cubepos(0,y,n), cr*cr
1127 #ifdef STANDALONE_SOLVER
1128 , "intersectional analysis,"
1129 " block (%d,%d) vs row %d",
1130 1+x/r, 1+y%r, 1+YUNTRANS(y)
1133 diff = max(diff, DIFF_INTERSECT);
1138 * Intersectional analysis, columns vs blocks.
1140 for (x = 0; x < cr; x++)
1141 for (y = 0; y < r; y++)
1142 for (n = 1; n <= cr; n++)
1143 if (!usage->col[x*cr+n-1] &&
1144 !usage->blk[(y*c+(x/r))*cr+n-1] &&
1145 (nsolve_intersect(usage, cubepos(x,0,n), cr,
1146 cubepos((x/r)*r,y,n), r*cr
1147 #ifdef STANDALONE_SOLVER
1148 , "intersectional analysis,"
1149 " column %d vs block (%d,%d)",
1153 nsolve_intersect(usage, cubepos((x/r)*r,y,n), r*cr,
1155 #ifdef STANDALONE_SOLVER
1156 , "intersectional analysis,"
1157 " block (%d,%d) vs column %d",
1161 diff = max(diff, DIFF_INTERSECT);
1166 * Blockwise set elimination.
1168 for (x = 0; x < cr; x += r)
1169 for (y = 0; y < r; y++)
1170 if (nsolve_set(usage, cubepos(x,y,1), r*cr, 1
1171 #ifdef STANDALONE_SOLVER
1172 , "set elimination, block (%d,%d)", 1+x/r, 1+y
1175 diff = max(diff, DIFF_SET);
1180 * Row-wise set elimination.
1182 for (y = 0; y < cr; y++)
1183 if (nsolve_set(usage, cubepos(0,y,1), cr*cr, 1
1184 #ifdef STANDALONE_SOLVER
1185 , "set elimination, row %d", 1+YUNTRANS(y)
1188 diff = max(diff, DIFF_SET);
1193 * Column-wise set elimination.
1195 for (x = 0; x < cr; x++)
1196 if (nsolve_set(usage, cubepos(x,0,1), cr, 1
1197 #ifdef STANDALONE_SOLVER
1198 , "set elimination, column %d", 1+x
1201 diff = max(diff, DIFF_SET);
1206 * If we reach here, we have made no deductions in this
1207 * iteration, so the algorithm terminates.
1218 for (x = 0; x < cr; x++)
1219 for (y = 0; y < cr; y++)
1221 return DIFF_IMPOSSIBLE;
1225 /* ----------------------------------------------------------------------
1226 * End of non-recursive solver code.
1230 * Check whether a grid contains a valid complete puzzle.
1232 static int check_valid(int c, int r, digit *grid)
1235 unsigned char *used;
1238 used = snewn(cr, unsigned char);
1241 * Check that each row contains precisely one of everything.
1243 for (y = 0; y < cr; y++) {
1244 memset(used, FALSE, cr);
1245 for (x = 0; x < cr; x++)
1246 if (grid[y*cr+x] > 0 && grid[y*cr+x] <= cr)
1247 used[grid[y*cr+x]-1] = TRUE;
1248 for (n = 0; n < cr; n++)
1256 * Check that each column contains precisely one of everything.
1258 for (x = 0; x < cr; x++) {
1259 memset(used, FALSE, cr);
1260 for (y = 0; y < cr; y++)
1261 if (grid[y*cr+x] > 0 && grid[y*cr+x] <= cr)
1262 used[grid[y*cr+x]-1] = TRUE;
1263 for (n = 0; n < cr; n++)
1271 * Check that each block contains precisely one of everything.
1273 for (x = 0; x < cr; x += r) {
1274 for (y = 0; y < cr; y += c) {
1276 memset(used, FALSE, cr);
1277 for (xx = x; xx < x+r; xx++)
1278 for (yy = 0; yy < y+c; yy++)
1279 if (grid[yy*cr+xx] > 0 && grid[yy*cr+xx] <= cr)
1280 used[grid[yy*cr+xx]-1] = TRUE;
1281 for (n = 0; n < cr; n++)
1293 static void symmetry_limit(game_params *params, int *xlim, int *ylim, int s)
1295 int c = params->c, r = params->r, cr = c*r;
1307 *xlim = *ylim = (cr+1) / 2;
1312 static int symmetries(game_params *params, int x, int y, int *output, int s)
1314 int c = params->c, r = params->r, cr = c*r;
1323 break; /* just x,y is all we need */
1328 *output++ = cr - 1 - x;
1333 *output++ = cr - 1 - y;
1337 *output++ = cr - 1 - y;
1342 *output++ = cr - 1 - x;
1348 *output++ = cr - 1 - x;
1349 *output++ = cr - 1 - y;
1357 struct game_aux_info {
1362 static char *new_game_seed(game_params *params, random_state *rs,
1363 game_aux_info **aux)
1365 int c = params->c, r = params->r, cr = c*r;
1367 digit *grid, *grid2;
1368 struct xy { int x, y; } *locs;
1372 int coords[16], ncoords;
1374 int maxdiff, recursing;
1377 * Adjust the maximum difficulty level to be consistent with
1378 * the puzzle size: all 2x2 puzzles appear to be Trivial
1379 * (DIFF_BLOCK) so we cannot hold out for even a Basic
1380 * (DIFF_SIMPLE) one.
1382 maxdiff = params->diff;
1383 if (c == 2 && r == 2)
1384 maxdiff = DIFF_BLOCK;
1386 grid = snewn(area, digit);
1387 locs = snewn(area, struct xy);
1388 grid2 = snewn(area, digit);
1391 * Loop until we get a grid of the required difficulty. This is
1392 * nasty, but it seems to be unpleasantly hard to generate
1393 * difficult grids otherwise.
1397 * Start the recursive solver with an empty grid to generate a
1398 * random solved state.
1400 memset(grid, 0, area);
1401 ret = rsolve(c, r, grid, rs, 1);
1403 assert(check_valid(c, r, grid));
1406 * Save the solved grid in the aux_info.
1409 game_aux_info *ai = snew(game_aux_info);
1412 ai->grid = snewn(cr * cr, digit);
1413 memcpy(ai->grid, grid, cr * cr * sizeof(digit));
1418 * Now we have a solved grid, start removing things from it
1419 * while preserving solubility.
1421 symmetry_limit(params, &xlim, &ylim, params->symm);
1427 * Iterate over the grid and enumerate all the filled
1428 * squares we could empty.
1432 for (x = 0; x < xlim; x++)
1433 for (y = 0; y < ylim; y++)
1441 * Now shuffle that list.
1443 for (i = nlocs; i > 1; i--) {
1444 int p = random_upto(rs, i);
1446 struct xy t = locs[p];
1447 locs[p] = locs[i-1];
1453 * Now loop over the shuffled list and, for each element,
1454 * see whether removing that element (and its reflections)
1455 * from the grid will still leave the grid soluble by
1458 for (i = 0; i < nlocs; i++) {
1464 memcpy(grid2, grid, area);
1465 ncoords = symmetries(params, x, y, coords, params->symm);
1466 for (j = 0; j < ncoords; j++)
1467 grid2[coords[2*j+1]*cr+coords[2*j]] = 0;
1470 ret = (rsolve(c, r, grid2, NULL, 2) == 1);
1472 ret = (nsolve(c, r, grid2) <= maxdiff);
1475 for (j = 0; j < ncoords; j++)
1476 grid[coords[2*j+1]*cr+coords[2*j]] = 0;
1483 * There was nothing we could remove without
1484 * destroying solvability. If we're trying to
1485 * generate a recursion-only grid and haven't
1486 * switched over to rsolve yet, we now do;
1487 * otherwise we give up.
1489 if (maxdiff == DIFF_RECURSIVE && !recursing) {
1497 memcpy(grid2, grid, area);
1498 } while (nsolve(c, r, grid2) < maxdiff);
1504 * Now we have the grid as it will be presented to the user.
1505 * Encode it in a game seed.
1511 seed = snewn(5 * area, char);
1514 for (i = 0; i <= area; i++) {
1515 int n = (i < area ? grid[i] : -1);
1522 int c = 'a' - 1 + run;
1526 run -= c - ('a' - 1);
1530 * If there's a number in the very top left or
1531 * bottom right, there's no point putting an
1532 * unnecessary _ before or after it.
1534 if (p > seed && n > 0)
1538 p += sprintf(p, "%d", n);
1542 assert(p - seed < 5 * area);
1544 seed = sresize(seed, p - seed, char);
1552 static void game_free_aux_info(game_aux_info *aux)
1558 static char *validate_seed(game_params *params, char *seed)
1560 int area = params->r * params->r * params->c * params->c;
1565 if (n >= 'a' && n <= 'z') {
1566 squares += n - 'a' + 1;
1567 } else if (n == '_') {
1569 } else if (n > '0' && n <= '9') {
1571 while (*seed >= '0' && *seed <= '9')
1574 return "Invalid character in game specification";
1578 return "Not enough data to fill grid";
1581 return "Too much data to fit in grid";
1586 static game_state *new_game(game_params *params, char *seed)
1588 game_state *state = snew(game_state);
1589 int c = params->c, r = params->r, cr = c*r, area = cr * cr;
1592 state->c = params->c;
1593 state->r = params->r;
1595 state->grid = snewn(area, digit);
1596 state->immutable = snewn(area, unsigned char);
1597 memset(state->immutable, FALSE, area);
1599 state->completed = state->cheated = FALSE;
1604 if (n >= 'a' && n <= 'z') {
1605 int run = n - 'a' + 1;
1606 assert(i + run <= area);
1608 state->grid[i++] = 0;
1609 } else if (n == '_') {
1611 } else if (n > '0' && n <= '9') {
1613 state->immutable[i] = TRUE;
1614 state->grid[i++] = atoi(seed-1);
1615 while (*seed >= '0' && *seed <= '9')
1618 assert(!"We can't get here");
1626 static game_state *dup_game(game_state *state)
1628 game_state *ret = snew(game_state);
1629 int c = state->c, r = state->r, cr = c*r, area = cr * cr;
1634 ret->grid = snewn(area, digit);
1635 memcpy(ret->grid, state->grid, area);
1637 ret->immutable = snewn(area, unsigned char);
1638 memcpy(ret->immutable, state->immutable, area);
1640 ret->completed = state->completed;
1641 ret->cheated = state->cheated;
1646 static void free_game(game_state *state)
1648 sfree(state->immutable);
1653 static game_state *solve_game(game_state *state, game_aux_info *ai,
1657 int c = state->c, r = state->r, cr = c*r;
1660 ret = dup_game(state);
1661 ret->completed = ret->cheated = TRUE;
1664 * If we already have the solution in the aux_info, save
1665 * ourselves some time.
1671 memcpy(ret->grid, ai->grid, cr * cr * sizeof(digit));
1674 rsolve_ret = rsolve(c, r, ret->grid, NULL, 2);
1676 if (rsolve_ret != 1) {
1678 if (rsolve_ret == 0)
1679 *error = "No solution exists for this puzzle";
1681 *error = "Multiple solutions exist for this puzzle";
1689 static char *grid_text_format(int c, int r, digit *grid)
1697 * There are cr lines of digits, plus r-1 lines of block
1698 * separators. Each line contains cr digits, cr-1 separating
1699 * spaces, and c-1 two-character block separators. Thus, the
1700 * total length of a line is 2*cr+2*c-3 (not counting the
1701 * newline), and there are cr+r-1 of them.
1703 maxlen = (cr+r-1) * (2*cr+2*c-2);
1704 ret = snewn(maxlen+1, char);
1707 for (y = 0; y < cr; y++) {
1708 for (x = 0; x < cr; x++) {
1709 int ch = grid[y * cr + x];
1719 if ((x+1) % r == 0) {
1726 if (y+1 < cr && (y+1) % c == 0) {
1727 for (x = 0; x < cr; x++) {
1731 if ((x+1) % r == 0) {
1741 assert(p - ret == maxlen);
1746 static char *game_text_format(game_state *state)
1748 return grid_text_format(state->c, state->r, state->grid);
1753 * These are the coordinates of the currently highlighted
1754 * square on the grid, or -1,-1 if there isn't one. When there
1755 * is, pressing a valid number or letter key or Space will
1756 * enter that number or letter in the grid.
1761 static game_ui *new_ui(game_state *state)
1763 game_ui *ui = snew(game_ui);
1765 ui->hx = ui->hy = -1;
1770 static void free_ui(game_ui *ui)
1775 static game_state *make_move(game_state *from, game_ui *ui, int x, int y,
1778 int c = from->c, r = from->r, cr = c*r;
1782 tx = (x + TILE_SIZE - BORDER) / TILE_SIZE - 1;
1783 ty = (y + TILE_SIZE - BORDER) / TILE_SIZE - 1;
1785 if (tx >= 0 && tx < cr && ty >= 0 && ty < cr && button == LEFT_BUTTON) {
1786 if (tx == ui->hx && ty == ui->hy) {
1787 ui->hx = ui->hy = -1;
1792 return from; /* UI activity occurred */
1795 if (ui->hx != -1 && ui->hy != -1 &&
1796 ((button >= '1' && button <= '9' && button - '0' <= cr) ||
1797 (button >= 'a' && button <= 'z' && button - 'a' + 10 <= cr) ||
1798 (button >= 'A' && button <= 'Z' && button - 'A' + 10 <= cr) ||
1800 int n = button - '0';
1801 if (button >= 'A' && button <= 'Z')
1802 n = button - 'A' + 10;
1803 if (button >= 'a' && button <= 'z')
1804 n = button - 'a' + 10;
1808 if (from->immutable[ui->hy*cr+ui->hx])
1809 return NULL; /* can't overwrite this square */
1811 ret = dup_game(from);
1812 ret->grid[ui->hy*cr+ui->hx] = n;
1813 ui->hx = ui->hy = -1;
1816 * We've made a real change to the grid. Check to see
1817 * if the game has been completed.
1819 if (!ret->completed && check_valid(c, r, ret->grid)) {
1820 ret->completed = TRUE;
1823 return ret; /* made a valid move */
1829 /* ----------------------------------------------------------------------
1833 struct game_drawstate {
1840 #define XSIZE(cr) ((cr) * TILE_SIZE + 2*BORDER + 1)
1841 #define YSIZE(cr) ((cr) * TILE_SIZE + 2*BORDER + 1)
1843 static void game_size(game_params *params, int *x, int *y)
1845 int c = params->c, r = params->r, cr = c*r;
1851 static float *game_colours(frontend *fe, game_state *state, int *ncolours)
1853 float *ret = snewn(3 * NCOLOURS, float);
1855 frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);
1857 ret[COL_GRID * 3 + 0] = 0.0F;
1858 ret[COL_GRID * 3 + 1] = 0.0F;
1859 ret[COL_GRID * 3 + 2] = 0.0F;
1861 ret[COL_CLUE * 3 + 0] = 0.0F;
1862 ret[COL_CLUE * 3 + 1] = 0.0F;
1863 ret[COL_CLUE * 3 + 2] = 0.0F;
1865 ret[COL_USER * 3 + 0] = 0.0F;
1866 ret[COL_USER * 3 + 1] = 0.6F * ret[COL_BACKGROUND * 3 + 1];
1867 ret[COL_USER * 3 + 2] = 0.0F;
1869 ret[COL_HIGHLIGHT * 3 + 0] = 0.85F * ret[COL_BACKGROUND * 3 + 0];
1870 ret[COL_HIGHLIGHT * 3 + 1] = 0.85F * ret[COL_BACKGROUND * 3 + 1];
1871 ret[COL_HIGHLIGHT * 3 + 2] = 0.85F * ret[COL_BACKGROUND * 3 + 2];
1873 *ncolours = NCOLOURS;
1877 static game_drawstate *game_new_drawstate(game_state *state)
1879 struct game_drawstate *ds = snew(struct game_drawstate);
1880 int c = state->c, r = state->r, cr = c*r;
1882 ds->started = FALSE;
1886 ds->grid = snewn(cr*cr, digit);
1887 memset(ds->grid, 0, cr*cr);
1888 ds->hl = snewn(cr*cr, unsigned char);
1889 memset(ds->hl, 0, cr*cr);
1894 static void game_free_drawstate(game_drawstate *ds)
1901 static void draw_number(frontend *fe, game_drawstate *ds, game_state *state,
1902 int x, int y, int hl)
1904 int c = state->c, r = state->r, cr = c*r;
1909 if (ds->grid[y*cr+x] == state->grid[y*cr+x] && ds->hl[y*cr+x] == hl)
1910 return; /* no change required */
1912 tx = BORDER + x * TILE_SIZE + 2;
1913 ty = BORDER + y * TILE_SIZE + 2;
1929 clip(fe, cx, cy, cw, ch);
1931 /* background needs erasing? */
1932 if (ds->grid[y*cr+x] || ds->hl[y*cr+x] != hl)
1933 draw_rect(fe, cx, cy, cw, ch, hl ? COL_HIGHLIGHT : COL_BACKGROUND);
1935 /* new number needs drawing? */
1936 if (state->grid[y*cr+x]) {
1938 str[0] = state->grid[y*cr+x] + '0';
1940 str[0] += 'a' - ('9'+1);
1941 draw_text(fe, tx + TILE_SIZE/2, ty + TILE_SIZE/2,
1942 FONT_VARIABLE, TILE_SIZE/2, ALIGN_VCENTRE | ALIGN_HCENTRE,
1943 state->immutable[y*cr+x] ? COL_CLUE : COL_USER, str);
1948 draw_update(fe, cx, cy, cw, ch);
1950 ds->grid[y*cr+x] = state->grid[y*cr+x];
1951 ds->hl[y*cr+x] = hl;
1954 static void game_redraw(frontend *fe, game_drawstate *ds, game_state *oldstate,
1955 game_state *state, int dir, game_ui *ui,
1956 float animtime, float flashtime)
1958 int c = state->c, r = state->r, cr = c*r;
1963 * The initial contents of the window are not guaranteed
1964 * and can vary with front ends. To be on the safe side,
1965 * all games should start by drawing a big
1966 * background-colour rectangle covering the whole window.
1968 draw_rect(fe, 0, 0, XSIZE(cr), YSIZE(cr), COL_BACKGROUND);
1973 for (x = 0; x <= cr; x++) {
1974 int thick = (x % r ? 0 : 1);
1975 draw_rect(fe, BORDER + x*TILE_SIZE - thick, BORDER-1,
1976 1+2*thick, cr*TILE_SIZE+3, COL_GRID);
1978 for (y = 0; y <= cr; y++) {
1979 int thick = (y % c ? 0 : 1);
1980 draw_rect(fe, BORDER-1, BORDER + y*TILE_SIZE - thick,
1981 cr*TILE_SIZE+3, 1+2*thick, COL_GRID);
1986 * Draw any numbers which need redrawing.
1988 for (x = 0; x < cr; x++) {
1989 for (y = 0; y < cr; y++) {
1990 draw_number(fe, ds, state, x, y,
1991 (x == ui->hx && y == ui->hy) ||
1993 (flashtime <= FLASH_TIME/3 ||
1994 flashtime >= FLASH_TIME*2/3)));
1999 * Update the _entire_ grid if necessary.
2002 draw_update(fe, 0, 0, XSIZE(cr), YSIZE(cr));
2007 static float game_anim_length(game_state *oldstate, game_state *newstate,
2013 static float game_flash_length(game_state *oldstate, game_state *newstate,
2016 if (!oldstate->completed && newstate->completed &&
2017 !oldstate->cheated && !newstate->cheated)
2022 static int game_wants_statusbar(void)
2028 #define thegame solo
2031 const struct game thegame = {
2032 "Solo", "games.solo",
2039 TRUE, game_configure, custom_params,
2048 TRUE, game_text_format,
2055 game_free_drawstate,
2059 game_wants_statusbar,
2062 #ifdef STANDALONE_SOLVER
2065 * gcc -DSTANDALONE_SOLVER -o solosolver solo.c malloc.c
2068 void frontend_default_colour(frontend *fe, float *output) {}
2069 void draw_text(frontend *fe, int x, int y, int fonttype, int fontsize,
2070 int align, int colour, char *text) {}
2071 void draw_rect(frontend *fe, int x, int y, int w, int h, int colour) {}
2072 void draw_line(frontend *fe, int x1, int y1, int x2, int y2, int colour) {}
2073 void draw_polygon(frontend *fe, int *coords, int npoints,
2074 int fill, int colour) {}
2075 void clip(frontend *fe, int x, int y, int w, int h) {}
2076 void unclip(frontend *fe) {}
2077 void start_draw(frontend *fe) {}
2078 void draw_update(frontend *fe, int x, int y, int w, int h) {}
2079 void end_draw(frontend *fe) {}
2080 unsigned long random_bits(random_state *state, int bits)
2081 { assert(!"Shouldn't get randomness"); return 0; }
2082 unsigned long random_upto(random_state *state, unsigned long limit)
2083 { assert(!"Shouldn't get randomness"); return 0; }
2085 void fatal(char *fmt, ...)
2089 fprintf(stderr, "fatal error: ");
2092 vfprintf(stderr, fmt, ap);
2095 fprintf(stderr, "\n");
2099 int main(int argc, char **argv)
2104 char *id = NULL, *seed, *err;
2108 while (--argc > 0) {
2110 if (!strcmp(p, "-r")) {
2112 } else if (!strcmp(p, "-n")) {
2114 } else if (!strcmp(p, "-v")) {
2115 solver_show_working = TRUE;
2117 } else if (!strcmp(p, "-g")) {
2120 } else if (*p == '-') {
2121 fprintf(stderr, "%s: unrecognised option `%s'\n", argv[0]);
2129 fprintf(stderr, "usage: %s [-n | -r | -g | -v] <game_id>\n", argv[0]);
2133 seed = strchr(id, ':');
2135 fprintf(stderr, "%s: game id expects a colon in it\n", argv[0]);
2140 p = decode_params(id);
2141 err = validate_seed(p, seed);
2143 fprintf(stderr, "%s: %s\n", argv[0], err);
2146 s = new_game(p, seed);
2149 int ret = rsolve(p->c, p->r, s->grid, NULL, 2);
2151 fprintf(stderr, "%s: rsolve: multiple solutions detected\n",
2155 int ret = nsolve(p->c, p->r, s->grid);
2157 if (ret == DIFF_IMPOSSIBLE) {
2159 * Now resort to rsolve to determine whether it's
2162 ret = rsolve(p->c, p->r, s->grid, NULL, 2);
2164 ret = DIFF_IMPOSSIBLE;
2166 ret = DIFF_RECURSIVE;
2168 ret = DIFF_AMBIGUOUS;
2170 printf("Difficulty rating: %s\n",
2171 ret==DIFF_BLOCK ? "Trivial (blockwise positional elimination only)":
2172 ret==DIFF_SIMPLE ? "Basic (row/column/number elimination required)":
2173 ret==DIFF_INTERSECT ? "Intermediate (intersectional analysis required)":
2174 ret==DIFF_SET ? "Advanced (set elimination required)":
2175 ret==DIFF_RECURSIVE ? "Unreasonable (guesswork and backtracking required)":
2176 ret==DIFF_AMBIGUOUS ? "Ambiguous (multiple solutions exist)":
2177 ret==DIFF_IMPOSSIBLE ? "Impossible (no solution exists)":
2178 "INTERNAL ERROR: unrecognised difficulty code");
2182 printf("%s\n", grid_text_format(p->c, p->r, s->grid));