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 { "3x4 Basic", { 3, 4, SYMM_ROT2, DIFF_SIMPLE } },
148 { "4x4 Basic", { 4, 4, SYMM_ROT2, DIFF_SIMPLE } },
151 if (i < 0 || i >= lenof(presets))
154 *name = dupstr(presets[i].title);
155 *params = dup_params(&presets[i].params);
160 static game_params *decode_params(char const *string)
162 game_params *ret = default_params();
164 ret->c = ret->r = atoi(string);
165 ret->symm = SYMM_ROT2;
166 while (*string && isdigit((unsigned char)*string)) string++;
167 if (*string == 'x') {
169 ret->r = atoi(string);
170 while (*string && isdigit((unsigned char)*string)) string++;
173 if (*string == 'r' || *string == 'm' || *string == 'a') {
177 while (*string && isdigit((unsigned char)*string)) string++;
178 if (sc == 'm' && sn == 4)
179 ret->symm = SYMM_REF4;
180 if (sc == 'r' && sn == 4)
181 ret->symm = SYMM_ROT4;
182 if (sc == 'r' && sn == 2)
183 ret->symm = SYMM_ROT2;
185 ret->symm = SYMM_NONE;
186 } else if (*string == 'd') {
188 if (*string == 't') /* trivial */
189 string++, ret->diff = DIFF_BLOCK;
190 else if (*string == 'b') /* basic */
191 string++, ret->diff = DIFF_SIMPLE;
192 else if (*string == 'i') /* intermediate */
193 string++, ret->diff = DIFF_INTERSECT;
194 else if (*string == 'a') /* advanced */
195 string++, ret->diff = DIFF_SET;
197 string++; /* eat unknown character */
203 static char *encode_params(game_params *params)
208 * Symmetry is a game generation preference and hence is left
209 * out of the encoding. Users can add it back in as they see
212 sprintf(str, "%dx%d", params->c, params->r);
216 static config_item *game_configure(game_params *params)
221 ret = snewn(5, config_item);
223 ret[0].name = "Columns of sub-blocks";
224 ret[0].type = C_STRING;
225 sprintf(buf, "%d", params->c);
226 ret[0].sval = dupstr(buf);
229 ret[1].name = "Rows of sub-blocks";
230 ret[1].type = C_STRING;
231 sprintf(buf, "%d", params->r);
232 ret[1].sval = dupstr(buf);
235 ret[2].name = "Symmetry";
236 ret[2].type = C_CHOICES;
237 ret[2].sval = ":None:2-way rotation:4-way rotation:4-way mirror";
238 ret[2].ival = params->symm;
240 ret[3].name = "Difficulty";
241 ret[3].type = C_CHOICES;
242 ret[3].sval = ":Trivial:Basic:Intermediate:Advanced";
243 ret[3].ival = params->diff;
253 static game_params *custom_params(config_item *cfg)
255 game_params *ret = snew(game_params);
257 ret->c = atoi(cfg[0].sval);
258 ret->r = atoi(cfg[1].sval);
259 ret->symm = cfg[2].ival;
260 ret->diff = cfg[3].ival;
265 static char *validate_params(game_params *params)
267 if (params->c < 2 || params->r < 2)
268 return "Both dimensions must be at least 2";
269 if (params->c > ORDER_MAX || params->r > ORDER_MAX)
270 return "Dimensions greater than "STR(ORDER_MAX)" are not supported";
274 /* ----------------------------------------------------------------------
275 * Full recursive Solo solver.
277 * The algorithm for this solver is shamelessly copied from a
278 * Python solver written by Andrew Wilkinson (which is GPLed, but
279 * I've reused only ideas and no code). It mostly just does the
280 * obvious recursive thing: pick an empty square, put one of the
281 * possible digits in it, recurse until all squares are filled,
282 * backtrack and change some choices if necessary.
284 * The clever bit is that every time it chooses which square to
285 * fill in next, it does so by counting the number of _possible_
286 * numbers that can go in each square, and it prioritises so that
287 * it picks a square with the _lowest_ number of possibilities. The
288 * idea is that filling in lots of the obvious bits (particularly
289 * any squares with only one possibility) will cut down on the list
290 * of possibilities for other squares and hence reduce the enormous
291 * search space as much as possible as early as possible.
293 * In practice the algorithm appeared to work very well; run on
294 * sample problems from the Times it completed in well under a
295 * second on my G5 even when written in Python, and given an empty
296 * grid (so that in principle it would enumerate _all_ solved
297 * grids!) it found the first valid solution just as quickly. So
298 * with a bit more randomisation I see no reason not to use this as
303 * Internal data structure used in solver to keep track of
306 struct rsolve_coord { int x, y, r; };
307 struct rsolve_usage {
308 int c, r, cr; /* cr == c*r */
309 /* grid is a copy of the input grid, modified as we go along */
311 /* row[y*cr+n-1] TRUE if digit n has been placed in row y */
313 /* col[x*cr+n-1] TRUE if digit n has been placed in row x */
315 /* blk[(y*c+x)*cr+n-1] TRUE if digit n has been placed in block (x,y) */
317 /* This lists all the empty spaces remaining in the grid. */
318 struct rsolve_coord *spaces;
320 /* If we need randomisation in the solve, this is our random state. */
322 /* Number of solutions so far found, and maximum number we care about. */
327 * The real recursive step in the solving function.
329 static void rsolve_real(struct rsolve_usage *usage, digit *grid)
331 int c = usage->c, r = usage->r, cr = usage->cr;
332 int i, j, n, sx, sy, bestm, bestr;
336 * Firstly, check for completion! If there are no spaces left
337 * in the grid, we have a solution.
339 if (usage->nspaces == 0) {
342 * This is our first solution, so fill in the output grid.
344 memcpy(grid, usage->grid, cr * cr);
351 * Otherwise, there must be at least one space. Find the most
352 * constrained space, using the `r' field as a tie-breaker.
354 bestm = cr+1; /* so that any space will beat it */
357 for (j = 0; j < usage->nspaces; j++) {
358 int x = usage->spaces[j].x, y = usage->spaces[j].y;
362 * Find the number of digits that could go in this space.
365 for (n = 0; n < cr; n++)
366 if (!usage->row[y*cr+n] && !usage->col[x*cr+n] &&
367 !usage->blk[((y/c)*c+(x/r))*cr+n])
370 if (m < bestm || (m == bestm && usage->spaces[j].r < bestr)) {
372 bestr = usage->spaces[j].r;
380 * Swap that square into the final place in the spaces array,
381 * so that decrementing nspaces will remove it from the list.
383 if (i != usage->nspaces-1) {
384 struct rsolve_coord t;
385 t = usage->spaces[usage->nspaces-1];
386 usage->spaces[usage->nspaces-1] = usage->spaces[i];
387 usage->spaces[i] = t;
391 * Now we've decided which square to start our recursion at,
392 * simply go through all possible values, shuffling them
393 * randomly first if necessary.
395 digits = snewn(bestm, int);
397 for (n = 0; n < cr; n++)
398 if (!usage->row[sy*cr+n] && !usage->col[sx*cr+n] &&
399 !usage->blk[((sy/c)*c+(sx/r))*cr+n]) {
405 for (i = j; i > 1; i--) {
406 int p = random_upto(usage->rs, i);
409 digits[p] = digits[i-1];
415 /* And finally, go through the digit list and actually recurse. */
416 for (i = 0; i < j; i++) {
419 /* Update the usage structure to reflect the placing of this digit. */
420 usage->row[sy*cr+n-1] = usage->col[sx*cr+n-1] =
421 usage->blk[((sy/c)*c+(sx/r))*cr+n-1] = TRUE;
422 usage->grid[sy*cr+sx] = n;
425 /* Call the solver recursively. */
426 rsolve_real(usage, grid);
429 * If we have seen as many solutions as we need, terminate
430 * all processing immediately.
432 if (usage->solns >= usage->maxsolns)
435 /* Revert the usage structure. */
436 usage->row[sy*cr+n-1] = usage->col[sx*cr+n-1] =
437 usage->blk[((sy/c)*c+(sx/r))*cr+n-1] = FALSE;
438 usage->grid[sy*cr+sx] = 0;
446 * Entry point to solver. You give it dimensions and a starting
447 * grid, which is simply an array of N^4 digits. In that array, 0
448 * means an empty square, and 1..N mean a clue square.
450 * Return value is the number of solutions found; searching will
451 * stop after the provided `max'. (Thus, you can pass max==1 to
452 * indicate that you only care about finding _one_ solution, or
453 * max==2 to indicate that you want to know the difference between
454 * a unique and non-unique solution.) The input parameter `grid' is
455 * also filled in with the _first_ (or only) solution found by the
458 static int rsolve(int c, int r, digit *grid, random_state *rs, int max)
460 struct rsolve_usage *usage;
465 * Create an rsolve_usage structure.
467 usage = snew(struct rsolve_usage);
473 usage->grid = snewn(cr * cr, digit);
474 memcpy(usage->grid, grid, cr * cr);
476 usage->row = snewn(cr * cr, unsigned char);
477 usage->col = snewn(cr * cr, unsigned char);
478 usage->blk = snewn(cr * cr, unsigned char);
479 memset(usage->row, FALSE, cr * cr);
480 memset(usage->col, FALSE, cr * cr);
481 memset(usage->blk, FALSE, cr * cr);
483 usage->spaces = snewn(cr * cr, struct rsolve_coord);
487 usage->maxsolns = max;
492 * Now fill it in with data from the input grid.
494 for (y = 0; y < cr; y++) {
495 for (x = 0; x < cr; x++) {
496 int v = grid[y*cr+x];
498 usage->spaces[usage->nspaces].x = x;
499 usage->spaces[usage->nspaces].y = y;
501 usage->spaces[usage->nspaces].r = random_bits(rs, 31);
503 usage->spaces[usage->nspaces].r = usage->nspaces;
506 usage->row[y*cr+v-1] = TRUE;
507 usage->col[x*cr+v-1] = TRUE;
508 usage->blk[((y/c)*c+(x/r))*cr+v-1] = TRUE;
514 * Run the real recursive solving function.
516 rsolve_real(usage, grid);
520 * Clean up the usage structure now we have our answer.
522 sfree(usage->spaces);
535 /* ----------------------------------------------------------------------
536 * End of recursive solver code.
539 /* ----------------------------------------------------------------------
540 * Less capable non-recursive solver. This one is used to check
541 * solubility of a grid as we gradually remove numbers from it: by
542 * verifying a grid using this solver we can ensure it isn't _too_
543 * hard (e.g. does not actually require guessing and backtracking).
545 * It supports a variety of specific modes of reasoning. By
546 * enabling or disabling subsets of these modes we can arrange a
547 * range of difficulty levels.
551 * Modes of reasoning currently supported:
553 * - Positional elimination: a number must go in a particular
554 * square because all the other empty squares in a given
555 * row/col/blk are ruled out.
557 * - Numeric elimination: a square must have a particular number
558 * in because all the other numbers that could go in it are
561 * - Intersectional analysis: given two domains which overlap
562 * (hence one must be a block, and the other can be a row or
563 * col), if the possible locations for a particular number in
564 * one of the domains can be narrowed down to the overlap, then
565 * that number can be ruled out everywhere but the overlap in
566 * the other domain too.
568 * - Set elimination: if there is a subset of the empty squares
569 * within a domain such that the union of the possible numbers
570 * in that subset has the same size as the subset itself, then
571 * those numbers can be ruled out everywhere else in the domain.
572 * (For example, if there are five empty squares and the
573 * possible numbers in each are 12, 23, 13, 134 and 1345, then
574 * the first three empty squares form such a subset: the numbers
575 * 1, 2 and 3 _must_ be in those three squares in some
576 * permutation, and hence we can deduce none of them can be in
577 * the fourth or fifth squares.)
578 * + You can also see this the other way round, concentrating
579 * on numbers rather than squares: if there is a subset of
580 * the unplaced numbers within a domain such that the union
581 * of all their possible positions has the same size as the
582 * subset itself, then all other numbers can be ruled out for
583 * those positions. However, it turns out that this is
584 * exactly equivalent to the first formulation at all times:
585 * there is a 1-1 correspondence between suitable subsets of
586 * the unplaced numbers and suitable subsets of the unfilled
587 * places, found by taking the _complement_ of the union of
588 * the numbers' possible positions (or the spaces' possible
593 * Within this solver, I'm going to transform all y-coordinates by
594 * inverting the significance of the block number and the position
595 * within the block. That is, we will start with the top row of
596 * each block in order, then the second row of each block in order,
599 * This transformation has the enormous advantage that it means
600 * every row, column _and_ block is described by an arithmetic
601 * progression of coordinates within the cubic array, so that I can
602 * use the same very simple function to do blockwise, row-wise and
603 * column-wise elimination.
605 #define YTRANS(y) (((y)%c)*r+(y)/c)
606 #define YUNTRANS(y) (((y)%r)*c+(y)/r)
608 struct nsolve_usage {
611 * We set up a cubic array, indexed by x, y and digit; each
612 * element of this array is TRUE or FALSE according to whether
613 * or not that digit _could_ in principle go in that position.
615 * The way to index this array is cube[(x*cr+y)*cr+n-1].
616 * y-coordinates in here are transformed.
620 * This is the grid in which we write down our final
621 * deductions. y-coordinates in here are _not_ transformed.
625 * Now we keep track, at a slightly higher level, of what we
626 * have yet to work out, to prevent doing the same deduction
629 /* row[y*cr+n-1] TRUE if digit n has been placed in row y */
631 /* col[x*cr+n-1] TRUE if digit n has been placed in row x */
633 /* blk[(y*c+x)*cr+n-1] TRUE if digit n has been placed in block (x,y) */
636 #define cubepos(x,y,n) (((x)*usage->cr+(y))*usage->cr+(n)-1)
637 #define cube(x,y,n) (usage->cube[cubepos(x,y,n)])
640 * Function called when we are certain that a particular square has
641 * a particular number in it. The y-coordinate passed in here is
644 static void nsolve_place(struct nsolve_usage *usage, int x, int y, int n)
646 int c = usage->c, r = usage->r, cr = usage->cr;
652 * Rule out all other numbers in this square.
654 for (i = 1; i <= cr; i++)
659 * Rule out this number in all other positions in the row.
661 for (i = 0; i < cr; i++)
666 * Rule out this number in all other positions in the column.
668 for (i = 0; i < cr; i++)
673 * Rule out this number in all other positions in the block.
677 for (i = 0; i < r; i++)
678 for (j = 0; j < c; j++)
679 if (bx+i != x || by+j*r != y)
680 cube(bx+i,by+j*r,n) = FALSE;
683 * Enter the number in the result grid.
685 usage->grid[YUNTRANS(y)*cr+x] = n;
688 * Cross out this number from the list of numbers left to place
689 * in its row, its column and its block.
691 usage->row[y*cr+n-1] = usage->col[x*cr+n-1] =
692 usage->blk[((y%r)*c+(x/r))*cr+n-1] = TRUE;
695 static int nsolve_elim(struct nsolve_usage *usage, int start, int step
696 #ifdef STANDALONE_SOLVER
701 int c = usage->c, r = usage->r, cr = c*r;
705 * Count the number of set bits within this section of the
710 for (i = 0; i < cr; i++)
711 if (usage->cube[start+i*step]) {
725 if (!usage->grid[YUNTRANS(y)*cr+x]) {
726 #ifdef STANDALONE_SOLVER
727 if (solver_show_working) {
732 printf(":\n placing %d at (%d,%d)\n",
733 n, 1+x, 1+YUNTRANS(y));
736 nsolve_place(usage, x, y, n);
744 static int nsolve_intersect(struct nsolve_usage *usage,
745 int start1, int step1, int start2, int step2
746 #ifdef STANDALONE_SOLVER
751 int c = usage->c, r = usage->r, cr = c*r;
755 * Loop over the first domain and see if there's any set bit
756 * not also in the second.
758 for (i = 0; i < cr; i++) {
759 int p = start1+i*step1;
760 if (usage->cube[p] &&
761 !(p >= start2 && p < start2+cr*step2 &&
762 (p - start2) % step2 == 0))
763 return FALSE; /* there is, so we can't deduce */
767 * We have determined that all set bits in the first domain are
768 * within its overlap with the second. So loop over the second
769 * domain and remove all set bits that aren't also in that
770 * overlap; return TRUE iff we actually _did_ anything.
773 for (i = 0; i < cr; i++) {
774 int p = start2+i*step2;
775 if (usage->cube[p] &&
776 !(p >= start1 && p < start1+cr*step1 && (p - start1) % step1 == 0))
778 #ifdef STANDALONE_SOLVER
779 if (solver_show_working) {
795 printf(" ruling out %d at (%d,%d)\n",
796 pn, 1+px, 1+YUNTRANS(py));
799 ret = TRUE; /* we did something */
807 static int nsolve_set(struct nsolve_usage *usage,
808 int start, int step1, int step2
809 #ifdef STANDALONE_SOLVER
814 int c = usage->c, r = usage->r, cr = c*r;
816 unsigned char *grid = snewn(cr*cr, unsigned char);
817 unsigned char *rowidx = snewn(cr, unsigned char);
818 unsigned char *colidx = snewn(cr, unsigned char);
819 unsigned char *set = snewn(cr, unsigned char);
822 * We are passed a cr-by-cr matrix of booleans. Our first job
823 * is to winnow it by finding any definite placements - i.e.
824 * any row with a solitary 1 - and discarding that row and the
825 * column containing the 1.
827 memset(rowidx, TRUE, cr);
828 memset(colidx, TRUE, cr);
829 for (i = 0; i < cr; i++) {
830 int count = 0, first = -1;
831 for (j = 0; j < cr; j++)
832 if (usage->cube[start+i*step1+j*step2])
836 * This condition actually marks a completely insoluble
837 * (i.e. internally inconsistent) puzzle. We return and
838 * report no progress made.
843 rowidx[i] = colidx[first] = FALSE;
847 * Convert each of rowidx/colidx from a list of 0s and 1s to a
848 * list of the indices of the 1s.
850 for (i = j = 0; i < cr; i++)
854 for (i = j = 0; i < cr; i++)
860 * And create the smaller matrix.
862 for (i = 0; i < n; i++)
863 for (j = 0; j < n; j++)
864 grid[i*cr+j] = usage->cube[start+rowidx[i]*step1+colidx[j]*step2];
867 * Having done that, we now have a matrix in which every row
868 * has at least two 1s in. Now we search to see if we can find
869 * a rectangle of zeroes (in the set-theoretic sense of
870 * `rectangle', i.e. a subset of rows crossed with a subset of
871 * columns) whose width and height add up to n.
878 * We have a candidate set. If its size is <=1 or >=n-1
879 * then we move on immediately.
881 if (count > 1 && count < n-1) {
883 * The number of rows we need is n-count. See if we can
884 * find that many rows which each have a zero in all
885 * the positions listed in `set'.
888 for (i = 0; i < n; i++) {
890 for (j = 0; j < n; j++)
891 if (set[j] && grid[i*cr+j]) {
900 * We expect never to be able to get _more_ than
901 * n-count suitable rows: this would imply that (for
902 * example) there are four numbers which between them
903 * have at most three possible positions, and hence it
904 * indicates a faulty deduction before this point or
907 assert(rows <= n - count);
908 if (rows >= n - count) {
909 int progress = FALSE;
912 * We've got one! Now, for each row which _doesn't_
913 * satisfy the criterion, eliminate all its set
914 * bits in the positions _not_ listed in `set'.
915 * Return TRUE (meaning progress has been made) if
916 * we successfully eliminated anything at all.
918 * This involves referring back through
919 * rowidx/colidx in order to work out which actual
920 * positions in the cube to meddle with.
922 for (i = 0; i < n; i++) {
924 for (j = 0; j < n; j++)
925 if (set[j] && grid[i*cr+j]) {
930 for (j = 0; j < n; j++)
931 if (!set[j] && grid[i*cr+j]) {
932 int fpos = (start+rowidx[i]*step1+
934 #ifdef STANDALONE_SOLVER
935 if (solver_show_working) {
951 printf(" ruling out %d at (%d,%d)\n",
952 pn, 1+px, 1+YUNTRANS(py));
956 usage->cube[fpos] = FALSE;
972 * Binary increment: change the rightmost 0 to a 1, and
973 * change all 1s to the right of it to 0s.
976 while (i > 0 && set[i-1])
977 set[--i] = 0, count--;
979 set[--i] = 1, count++;
992 static int nsolve(int c, int r, digit *grid)
994 struct nsolve_usage *usage;
997 int diff = DIFF_BLOCK;
1000 * Set up a usage structure as a clean slate (everything
1003 usage = snew(struct nsolve_usage);
1007 usage->cube = snewn(cr*cr*cr, unsigned char);
1008 usage->grid = grid; /* write straight back to the input */
1009 memset(usage->cube, TRUE, cr*cr*cr);
1011 usage->row = snewn(cr * cr, unsigned char);
1012 usage->col = snewn(cr * cr, unsigned char);
1013 usage->blk = snewn(cr * cr, unsigned char);
1014 memset(usage->row, FALSE, cr * cr);
1015 memset(usage->col, FALSE, cr * cr);
1016 memset(usage->blk, FALSE, cr * cr);
1019 * Place all the clue numbers we are given.
1021 for (x = 0; x < cr; x++)
1022 for (y = 0; y < cr; y++)
1024 nsolve_place(usage, x, YTRANS(y), grid[y*cr+x]);
1027 * Now loop over the grid repeatedly trying all permitted modes
1028 * of reasoning. The loop terminates if we complete an
1029 * iteration without making any progress; we then return
1030 * failure or success depending on whether the grid is full or
1035 * I'd like to write `continue;' inside each of the
1036 * following loops, so that the solver returns here after
1037 * making some progress. However, I can't specify that I
1038 * want to continue an outer loop rather than the innermost
1039 * one, so I'm apologetically resorting to a goto.
1044 * Blockwise positional elimination.
1046 for (x = 0; x < cr; x += r)
1047 for (y = 0; y < r; y++)
1048 for (n = 1; n <= cr; n++)
1049 if (!usage->blk[(y*c+(x/r))*cr+n-1] &&
1050 nsolve_elim(usage, cubepos(x,y,n), r*cr
1051 #ifdef STANDALONE_SOLVER
1052 , "positional elimination,"
1053 " block (%d,%d)", 1+x/r, 1+y
1056 diff = max(diff, DIFF_BLOCK);
1061 * Row-wise positional elimination.
1063 for (y = 0; y < cr; y++)
1064 for (n = 1; n <= cr; n++)
1065 if (!usage->row[y*cr+n-1] &&
1066 nsolve_elim(usage, cubepos(0,y,n), cr*cr
1067 #ifdef STANDALONE_SOLVER
1068 , "positional elimination,"
1069 " row %d", 1+YUNTRANS(y)
1072 diff = max(diff, DIFF_SIMPLE);
1076 * Column-wise positional elimination.
1078 for (x = 0; x < cr; x++)
1079 for (n = 1; n <= cr; n++)
1080 if (!usage->col[x*cr+n-1] &&
1081 nsolve_elim(usage, cubepos(x,0,n), cr
1082 #ifdef STANDALONE_SOLVER
1083 , "positional elimination," " column %d", 1+x
1086 diff = max(diff, DIFF_SIMPLE);
1091 * Numeric elimination.
1093 for (x = 0; x < cr; x++)
1094 for (y = 0; y < cr; y++)
1095 if (!usage->grid[YUNTRANS(y)*cr+x] &&
1096 nsolve_elim(usage, cubepos(x,y,1), 1
1097 #ifdef STANDALONE_SOLVER
1098 , "numeric elimination at (%d,%d)", 1+x,
1102 diff = max(diff, DIFF_SIMPLE);
1107 * Intersectional analysis, rows vs blocks.
1109 for (y = 0; y < cr; y++)
1110 for (x = 0; x < cr; x += r)
1111 for (n = 1; n <= cr; n++)
1112 if (!usage->row[y*cr+n-1] &&
1113 !usage->blk[((y%r)*c+(x/r))*cr+n-1] &&
1114 (nsolve_intersect(usage, cubepos(0,y,n), cr*cr,
1115 cubepos(x,y%r,n), r*cr
1116 #ifdef STANDALONE_SOLVER
1117 , "intersectional analysis,"
1118 " row %d vs block (%d,%d)",
1119 1+YUNTRANS(y), 1+x/r, 1+y%r
1122 nsolve_intersect(usage, cubepos(x,y%r,n), r*cr,
1123 cubepos(0,y,n), cr*cr
1124 #ifdef STANDALONE_SOLVER
1125 , "intersectional analysis,"
1126 " block (%d,%d) vs row %d",
1127 1+x/r, 1+y%r, 1+YUNTRANS(y)
1130 diff = max(diff, DIFF_INTERSECT);
1135 * Intersectional analysis, columns vs blocks.
1137 for (x = 0; x < cr; x++)
1138 for (y = 0; y < r; y++)
1139 for (n = 1; n <= cr; n++)
1140 if (!usage->col[x*cr+n-1] &&
1141 !usage->blk[(y*c+(x/r))*cr+n-1] &&
1142 (nsolve_intersect(usage, cubepos(x,0,n), cr,
1143 cubepos((x/r)*r,y,n), r*cr
1144 #ifdef STANDALONE_SOLVER
1145 , "intersectional analysis,"
1146 " column %d vs block (%d,%d)",
1150 nsolve_intersect(usage, cubepos((x/r)*r,y,n), r*cr,
1152 #ifdef STANDALONE_SOLVER
1153 , "intersectional analysis,"
1154 " block (%d,%d) vs column %d",
1158 diff = max(diff, DIFF_INTERSECT);
1163 * Blockwise set elimination.
1165 for (x = 0; x < cr; x += r)
1166 for (y = 0; y < r; y++)
1167 if (nsolve_set(usage, cubepos(x,y,1), r*cr, 1
1168 #ifdef STANDALONE_SOLVER
1169 , "set elimination, block (%d,%d)", 1+x/r, 1+y
1172 diff = max(diff, DIFF_SET);
1177 * Row-wise set elimination.
1179 for (y = 0; y < cr; y++)
1180 if (nsolve_set(usage, cubepos(0,y,1), cr*cr, 1
1181 #ifdef STANDALONE_SOLVER
1182 , "set elimination, row %d", 1+YUNTRANS(y)
1185 diff = max(diff, DIFF_SET);
1190 * Column-wise set elimination.
1192 for (x = 0; x < cr; x++)
1193 if (nsolve_set(usage, cubepos(x,0,1), cr, 1
1194 #ifdef STANDALONE_SOLVER
1195 , "set elimination, column %d", 1+x
1198 diff = max(diff, DIFF_SET);
1203 * If we reach here, we have made no deductions in this
1204 * iteration, so the algorithm terminates.
1215 for (x = 0; x < cr; x++)
1216 for (y = 0; y < cr; y++)
1218 return DIFF_IMPOSSIBLE;
1222 /* ----------------------------------------------------------------------
1223 * End of non-recursive solver code.
1227 * Check whether a grid contains a valid complete puzzle.
1229 static int check_valid(int c, int r, digit *grid)
1232 unsigned char *used;
1235 used = snewn(cr, unsigned char);
1238 * Check that each row contains precisely one of everything.
1240 for (y = 0; y < cr; y++) {
1241 memset(used, FALSE, cr);
1242 for (x = 0; x < cr; x++)
1243 if (grid[y*cr+x] > 0 && grid[y*cr+x] <= cr)
1244 used[grid[y*cr+x]-1] = TRUE;
1245 for (n = 0; n < cr; n++)
1253 * Check that each column contains precisely one of everything.
1255 for (x = 0; x < cr; x++) {
1256 memset(used, FALSE, cr);
1257 for (y = 0; y < cr; y++)
1258 if (grid[y*cr+x] > 0 && grid[y*cr+x] <= cr)
1259 used[grid[y*cr+x]-1] = TRUE;
1260 for (n = 0; n < cr; n++)
1268 * Check that each block contains precisely one of everything.
1270 for (x = 0; x < cr; x += r) {
1271 for (y = 0; y < cr; y += c) {
1273 memset(used, FALSE, cr);
1274 for (xx = x; xx < x+r; xx++)
1275 for (yy = 0; yy < y+c; yy++)
1276 if (grid[yy*cr+xx] > 0 && grid[yy*cr+xx] <= cr)
1277 used[grid[yy*cr+xx]-1] = TRUE;
1278 for (n = 0; n < cr; n++)
1290 static void symmetry_limit(game_params *params, int *xlim, int *ylim, int s)
1292 int c = params->c, r = params->r, cr = c*r;
1304 *xlim = *ylim = (cr+1) / 2;
1309 static int symmetries(game_params *params, int x, int y, int *output, int s)
1311 int c = params->c, r = params->r, cr = c*r;
1320 break; /* just x,y is all we need */
1325 *output++ = cr - 1 - x;
1330 *output++ = cr - 1 - y;
1334 *output++ = cr - 1 - y;
1339 *output++ = cr - 1 - x;
1345 *output++ = cr - 1 - x;
1346 *output++ = cr - 1 - y;
1354 struct game_aux_info {
1359 static char *new_game_seed(game_params *params, random_state *rs,
1360 game_aux_info **aux)
1362 int c = params->c, r = params->r, cr = c*r;
1364 digit *grid, *grid2;
1365 struct xy { int x, y; } *locs;
1369 int coords[16], ncoords;
1374 * Adjust the maximum difficulty level to be consistent with
1375 * the puzzle size: all 2x2 puzzles appear to be Trivial
1376 * (DIFF_BLOCK) so we cannot hold out for even a Basic
1377 * (DIFF_SIMPLE) one.
1379 maxdiff = params->diff;
1380 if (c == 2 && r == 2)
1381 maxdiff = DIFF_BLOCK;
1383 grid = snewn(area, digit);
1384 locs = snewn(area, struct xy);
1385 grid2 = snewn(area, digit);
1388 * Loop until we get a grid of the required difficulty. This is
1389 * nasty, but it seems to be unpleasantly hard to generate
1390 * difficult grids otherwise.
1394 * Start the recursive solver with an empty grid to generate a
1395 * random solved state.
1397 memset(grid, 0, area);
1398 ret = rsolve(c, r, grid, rs, 1);
1400 assert(check_valid(c, r, grid));
1403 * Save the solved grid in the aux_info.
1406 game_aux_info *ai = snew(game_aux_info);
1409 ai->grid = snewn(cr * cr, digit);
1410 memcpy(ai->grid, grid, cr * cr * sizeof(digit));
1415 * Now we have a solved grid, start removing things from it
1416 * while preserving solubility.
1418 symmetry_limit(params, &xlim, &ylim, params->symm);
1423 * Iterate over the grid and enumerate all the filled
1424 * squares we could empty.
1428 for (x = 0; x < xlim; x++)
1429 for (y = 0; y < ylim; y++)
1437 * Now shuffle that list.
1439 for (i = nlocs; i > 1; i--) {
1440 int p = random_upto(rs, i);
1442 struct xy t = locs[p];
1443 locs[p] = locs[i-1];
1449 * Now loop over the shuffled list and, for each element,
1450 * see whether removing that element (and its reflections)
1451 * from the grid will still leave the grid soluble by
1454 for (i = 0; i < nlocs; i++) {
1458 memcpy(grid2, grid, area);
1459 ncoords = symmetries(params, x, y, coords, params->symm);
1460 for (j = 0; j < ncoords; j++)
1461 grid2[coords[2*j+1]*cr+coords[2*j]] = 0;
1463 if (nsolve(c, r, grid2) <= maxdiff) {
1464 for (j = 0; j < ncoords; j++)
1465 grid[coords[2*j+1]*cr+coords[2*j]] = 0;
1472 * There was nothing we could remove without destroying
1479 memcpy(grid2, grid, area);
1480 } while (nsolve(c, r, grid2) != maxdiff);
1486 * Now we have the grid as it will be presented to the user.
1487 * Encode it in a game seed.
1493 seed = snewn(5 * area, char);
1496 for (i = 0; i <= area; i++) {
1497 int n = (i < area ? grid[i] : -1);
1504 int c = 'a' - 1 + run;
1508 run -= c - ('a' - 1);
1512 * If there's a number in the very top left or
1513 * bottom right, there's no point putting an
1514 * unnecessary _ before or after it.
1516 if (p > seed && n > 0)
1520 p += sprintf(p, "%d", n);
1524 assert(p - seed < 5 * area);
1526 seed = sresize(seed, p - seed, char);
1534 static void game_free_aux_info(game_aux_info *aux)
1540 static char *validate_seed(game_params *params, char *seed)
1542 int area = params->r * params->r * params->c * params->c;
1547 if (n >= 'a' && n <= 'z') {
1548 squares += n - 'a' + 1;
1549 } else if (n == '_') {
1551 } else if (n > '0' && n <= '9') {
1553 while (*seed >= '0' && *seed <= '9')
1556 return "Invalid character in game specification";
1560 return "Not enough data to fill grid";
1563 return "Too much data to fit in grid";
1568 static game_state *new_game(game_params *params, char *seed)
1570 game_state *state = snew(game_state);
1571 int c = params->c, r = params->r, cr = c*r, area = cr * cr;
1574 state->c = params->c;
1575 state->r = params->r;
1577 state->grid = snewn(area, digit);
1578 state->immutable = snewn(area, unsigned char);
1579 memset(state->immutable, FALSE, area);
1581 state->completed = state->cheated = FALSE;
1586 if (n >= 'a' && n <= 'z') {
1587 int run = n - 'a' + 1;
1588 assert(i + run <= area);
1590 state->grid[i++] = 0;
1591 } else if (n == '_') {
1593 } else if (n > '0' && n <= '9') {
1595 state->immutable[i] = TRUE;
1596 state->grid[i++] = atoi(seed-1);
1597 while (*seed >= '0' && *seed <= '9')
1600 assert(!"We can't get here");
1608 static game_state *dup_game(game_state *state)
1610 game_state *ret = snew(game_state);
1611 int c = state->c, r = state->r, cr = c*r, area = cr * cr;
1616 ret->grid = snewn(area, digit);
1617 memcpy(ret->grid, state->grid, area);
1619 ret->immutable = snewn(area, unsigned char);
1620 memcpy(ret->immutable, state->immutable, area);
1622 ret->completed = state->completed;
1623 ret->cheated = state->cheated;
1628 static void free_game(game_state *state)
1630 sfree(state->immutable);
1635 static game_state *solve_game(game_state *state, game_aux_info *ai,
1639 int c = state->c, r = state->r, cr = c*r;
1642 ret = dup_game(state);
1643 ret->completed = ret->cheated = TRUE;
1646 * If we already have the solution in the aux_info, save
1647 * ourselves some time.
1653 memcpy(ret->grid, ai->grid, cr * cr * sizeof(digit));
1656 rsolve_ret = rsolve(c, r, ret->grid, NULL, 2);
1658 if (rsolve_ret != 1) {
1660 if (rsolve_ret == 0)
1661 *error = "No solution exists for this puzzle";
1663 *error = "Multiple solutions exist for this puzzle";
1671 static char *grid_text_format(int c, int r, digit *grid)
1679 * There are cr lines of digits, plus r-1 lines of block
1680 * separators. Each line contains cr digits, cr-1 separating
1681 * spaces, and c-1 two-character block separators. Thus, the
1682 * total length of a line is 2*cr+2*c-3 (not counting the
1683 * newline), and there are cr+r-1 of them.
1685 maxlen = (cr+r-1) * (2*cr+2*c-2);
1686 ret = snewn(maxlen+1, char);
1689 for (y = 0; y < cr; y++) {
1690 for (x = 0; x < cr; x++) {
1691 int ch = grid[y * cr + x];
1701 if ((x+1) % r == 0) {
1708 if (y+1 < cr && (y+1) % c == 0) {
1709 for (x = 0; x < cr; x++) {
1713 if ((x+1) % r == 0) {
1723 assert(p - ret == maxlen);
1728 static char *game_text_format(game_state *state)
1730 return grid_text_format(state->c, state->r, state->grid);
1735 * These are the coordinates of the currently highlighted
1736 * square on the grid, or -1,-1 if there isn't one. When there
1737 * is, pressing a valid number or letter key or Space will
1738 * enter that number or letter in the grid.
1743 static game_ui *new_ui(game_state *state)
1745 game_ui *ui = snew(game_ui);
1747 ui->hx = ui->hy = -1;
1752 static void free_ui(game_ui *ui)
1757 static game_state *make_move(game_state *from, game_ui *ui, int x, int y,
1760 int c = from->c, r = from->r, cr = c*r;
1764 tx = (x + TILE_SIZE - BORDER) / TILE_SIZE - 1;
1765 ty = (y + TILE_SIZE - BORDER) / TILE_SIZE - 1;
1767 if (tx >= 0 && tx < cr && ty >= 0 && ty < cr && button == LEFT_BUTTON) {
1768 if (tx == ui->hx && ty == ui->hy) {
1769 ui->hx = ui->hy = -1;
1774 return from; /* UI activity occurred */
1777 if (ui->hx != -1 && ui->hy != -1 &&
1778 ((button >= '1' && button <= '9' && button - '0' <= cr) ||
1779 (button >= 'a' && button <= 'z' && button - 'a' + 10 <= cr) ||
1780 (button >= 'A' && button <= 'Z' && button - 'A' + 10 <= cr) ||
1782 int n = button - '0';
1783 if (button >= 'A' && button <= 'Z')
1784 n = button - 'A' + 10;
1785 if (button >= 'a' && button <= 'z')
1786 n = button - 'a' + 10;
1790 if (from->immutable[ui->hy*cr+ui->hx])
1791 return NULL; /* can't overwrite this square */
1793 ret = dup_game(from);
1794 ret->grid[ui->hy*cr+ui->hx] = n;
1795 ui->hx = ui->hy = -1;
1798 * We've made a real change to the grid. Check to see
1799 * if the game has been completed.
1801 if (!ret->completed && check_valid(c, r, ret->grid)) {
1802 ret->completed = TRUE;
1805 return ret; /* made a valid move */
1811 /* ----------------------------------------------------------------------
1815 struct game_drawstate {
1822 #define XSIZE(cr) ((cr) * TILE_SIZE + 2*BORDER + 1)
1823 #define YSIZE(cr) ((cr) * TILE_SIZE + 2*BORDER + 1)
1825 static void game_size(game_params *params, int *x, int *y)
1827 int c = params->c, r = params->r, cr = c*r;
1833 static float *game_colours(frontend *fe, game_state *state, int *ncolours)
1835 float *ret = snewn(3 * NCOLOURS, float);
1837 frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);
1839 ret[COL_GRID * 3 + 0] = 0.0F;
1840 ret[COL_GRID * 3 + 1] = 0.0F;
1841 ret[COL_GRID * 3 + 2] = 0.0F;
1843 ret[COL_CLUE * 3 + 0] = 0.0F;
1844 ret[COL_CLUE * 3 + 1] = 0.0F;
1845 ret[COL_CLUE * 3 + 2] = 0.0F;
1847 ret[COL_USER * 3 + 0] = 0.0F;
1848 ret[COL_USER * 3 + 1] = 0.6F * ret[COL_BACKGROUND * 3 + 1];
1849 ret[COL_USER * 3 + 2] = 0.0F;
1851 ret[COL_HIGHLIGHT * 3 + 0] = 0.85F * ret[COL_BACKGROUND * 3 + 0];
1852 ret[COL_HIGHLIGHT * 3 + 1] = 0.85F * ret[COL_BACKGROUND * 3 + 1];
1853 ret[COL_HIGHLIGHT * 3 + 2] = 0.85F * ret[COL_BACKGROUND * 3 + 2];
1855 *ncolours = NCOLOURS;
1859 static game_drawstate *game_new_drawstate(game_state *state)
1861 struct game_drawstate *ds = snew(struct game_drawstate);
1862 int c = state->c, r = state->r, cr = c*r;
1864 ds->started = FALSE;
1868 ds->grid = snewn(cr*cr, digit);
1869 memset(ds->grid, 0, cr*cr);
1870 ds->hl = snewn(cr*cr, unsigned char);
1871 memset(ds->hl, 0, cr*cr);
1876 static void game_free_drawstate(game_drawstate *ds)
1883 static void draw_number(frontend *fe, game_drawstate *ds, game_state *state,
1884 int x, int y, int hl)
1886 int c = state->c, r = state->r, cr = c*r;
1891 if (ds->grid[y*cr+x] == state->grid[y*cr+x] && ds->hl[y*cr+x] == hl)
1892 return; /* no change required */
1894 tx = BORDER + x * TILE_SIZE + 2;
1895 ty = BORDER + y * TILE_SIZE + 2;
1911 clip(fe, cx, cy, cw, ch);
1913 /* background needs erasing? */
1914 if (ds->grid[y*cr+x] || ds->hl[y*cr+x] != hl)
1915 draw_rect(fe, cx, cy, cw, ch, hl ? COL_HIGHLIGHT : COL_BACKGROUND);
1917 /* new number needs drawing? */
1918 if (state->grid[y*cr+x]) {
1920 str[0] = state->grid[y*cr+x] + '0';
1922 str[0] += 'a' - ('9'+1);
1923 draw_text(fe, tx + TILE_SIZE/2, ty + TILE_SIZE/2,
1924 FONT_VARIABLE, TILE_SIZE/2, ALIGN_VCENTRE | ALIGN_HCENTRE,
1925 state->immutable[y*cr+x] ? COL_CLUE : COL_USER, str);
1930 draw_update(fe, cx, cy, cw, ch);
1932 ds->grid[y*cr+x] = state->grid[y*cr+x];
1933 ds->hl[y*cr+x] = hl;
1936 static void game_redraw(frontend *fe, game_drawstate *ds, game_state *oldstate,
1937 game_state *state, int dir, game_ui *ui,
1938 float animtime, float flashtime)
1940 int c = state->c, r = state->r, cr = c*r;
1945 * The initial contents of the window are not guaranteed
1946 * and can vary with front ends. To be on the safe side,
1947 * all games should start by drawing a big
1948 * background-colour rectangle covering the whole window.
1950 draw_rect(fe, 0, 0, XSIZE(cr), YSIZE(cr), COL_BACKGROUND);
1955 for (x = 0; x <= cr; x++) {
1956 int thick = (x % r ? 0 : 1);
1957 draw_rect(fe, BORDER + x*TILE_SIZE - thick, BORDER-1,
1958 1+2*thick, cr*TILE_SIZE+3, COL_GRID);
1960 for (y = 0; y <= cr; y++) {
1961 int thick = (y % c ? 0 : 1);
1962 draw_rect(fe, BORDER-1, BORDER + y*TILE_SIZE - thick,
1963 cr*TILE_SIZE+3, 1+2*thick, COL_GRID);
1968 * Draw any numbers which need redrawing.
1970 for (x = 0; x < cr; x++) {
1971 for (y = 0; y < cr; y++) {
1972 draw_number(fe, ds, state, x, y,
1973 (x == ui->hx && y == ui->hy) ||
1975 (flashtime <= FLASH_TIME/3 ||
1976 flashtime >= FLASH_TIME*2/3)));
1981 * Update the _entire_ grid if necessary.
1984 draw_update(fe, 0, 0, XSIZE(cr), YSIZE(cr));
1989 static float game_anim_length(game_state *oldstate, game_state *newstate,
1995 static float game_flash_length(game_state *oldstate, game_state *newstate,
1998 if (!oldstate->completed && newstate->completed &&
1999 !oldstate->cheated && !newstate->cheated)
2004 static int game_wants_statusbar(void)
2010 #define thegame solo
2013 const struct game thegame = {
2014 "Solo", "games.solo",
2021 TRUE, game_configure, custom_params,
2030 TRUE, game_text_format,
2037 game_free_drawstate,
2041 game_wants_statusbar,
2044 #ifdef STANDALONE_SOLVER
2047 * gcc -DSTANDALONE_SOLVER -o solosolver solo.c malloc.c
2050 void frontend_default_colour(frontend *fe, float *output) {}
2051 void draw_text(frontend *fe, int x, int y, int fonttype, int fontsize,
2052 int align, int colour, char *text) {}
2053 void draw_rect(frontend *fe, int x, int y, int w, int h, int colour) {}
2054 void draw_line(frontend *fe, int x1, int y1, int x2, int y2, int colour) {}
2055 void draw_polygon(frontend *fe, int *coords, int npoints,
2056 int fill, int colour) {}
2057 void clip(frontend *fe, int x, int y, int w, int h) {}
2058 void unclip(frontend *fe) {}
2059 void start_draw(frontend *fe) {}
2060 void draw_update(frontend *fe, int x, int y, int w, int h) {}
2061 void end_draw(frontend *fe) {}
2062 unsigned long random_bits(random_state *state, int bits)
2063 { assert(!"Shouldn't get randomness"); return 0; }
2064 unsigned long random_upto(random_state *state, unsigned long limit)
2065 { assert(!"Shouldn't get randomness"); return 0; }
2067 void fatal(char *fmt, ...)
2071 fprintf(stderr, "fatal error: ");
2074 vfprintf(stderr, fmt, ap);
2077 fprintf(stderr, "\n");
2081 int main(int argc, char **argv)
2086 char *id = NULL, *seed, *err;
2090 while (--argc > 0) {
2092 if (!strcmp(p, "-r")) {
2094 } else if (!strcmp(p, "-n")) {
2096 } else if (!strcmp(p, "-v")) {
2097 solver_show_working = TRUE;
2099 } else if (!strcmp(p, "-g")) {
2102 } else if (*p == '-') {
2103 fprintf(stderr, "%s: unrecognised option `%s'\n", argv[0]);
2111 fprintf(stderr, "usage: %s [-n | -r | -g | -v] <game_id>\n", argv[0]);
2115 seed = strchr(id, ':');
2117 fprintf(stderr, "%s: game id expects a colon in it\n", argv[0]);
2122 p = decode_params(id);
2123 err = validate_seed(p, seed);
2125 fprintf(stderr, "%s: %s\n", argv[0], err);
2128 s = new_game(p, seed);
2131 int ret = rsolve(p->c, p->r, s->grid, NULL, 2);
2133 fprintf(stderr, "%s: rsolve: multiple solutions detected\n",
2137 int ret = nsolve(p->c, p->r, s->grid);
2139 if (ret == DIFF_IMPOSSIBLE) {
2141 * Now resort to rsolve to determine whether it's
2144 ret = rsolve(p->c, p->r, s->grid, NULL, 2);
2146 ret = DIFF_IMPOSSIBLE;
2148 ret = DIFF_RECURSIVE;
2150 ret = DIFF_AMBIGUOUS;
2152 printf("Difficulty rating: %s\n",
2153 ret==DIFF_BLOCK ? "Trivial (blockwise positional elimination only)":
2154 ret==DIFF_SIMPLE ? "Basic (row/column/number elimination required)":
2155 ret==DIFF_INTERSECT ? "Intermediate (intersectional analysis required)":
2156 ret==DIFF_SET ? "Advanced (set elimination required)":
2157 ret==DIFF_RECURSIVE ? "Unreasonable (guesswork and backtracking required)":
2158 ret==DIFF_AMBIGUOUS ? "Ambiguous (multiple solutions exist)":
2159 ret==DIFF_IMPOSSIBLE ? "Impossible (no solution exists)":
2160 "INTERNAL ERROR: unrecognised difficulty code");
2164 printf("%s\n", grid_text_format(p->c, p->r, s->grid));