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Groups > comp.lang.c > #397458
| From | Tim Rentsch <tr.17687@z991.linuxsc.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Cookies in boxes - algorithmic challenge |
| Date | 2026-04-09 17:07 -0700 |
| Organization | A noiseless patient Spider |
| Message-ID | <86a4vbbruq.fsf@linuxsc.com> (permalink) |
| References | <20260401163447.000052de@yahoo.com> <20260409000116.0000461d@yahoo.com> |
Michael S <already5chosen@yahoo.com> writes:
> On Wed, 1 Apr 2026 16:34:47 +0300
> Michael S <already5chosen@yahoo.com> wrote:
>
> <snip>
>
> My solution #2.
> That is my own, with no proof preceding code. It went in other direction
> - from hacking the code to proving it later.
> It is pretty fast. Can be made faster yet by replication of some code
> and re-arrangement in the find() routine, but for purposes of
> illustration I wanted it short.
Just fyi.. I did some speed comparisons between the code below and
the compatible solver that I wrote. Your code is faster, scales
better, and also has better worst-case behavior (which is to say
that my code has worse worst-case behavior). So I think the timing
numbers I was seeing before may have been just the result of being
lucky in the draw of random numbers.
> #include <stdint.h>
> #include <string.h>
> #include <stdbool.h>
>
> #include "solver.h"
>
> static
> uint8_t solver_find(
> const uint8_t b_idx[N_BOXES][N_BOXES],
> uint8_t result[N_BOXES],
> const uint8_t free[N_BOXES],
> int n_free,
> uint8_t v,
> const uint8_t bx[N_BOXES][BOX_SIZE])
> {
> typedef struct {
> uint8_t parent, bi;
> } db_rec;
> db_rec db[N_BOXES];
> bool valid[N_BOXES] = {0};
> uint8_t que[N_BOXES], *wr = que, *rd = que;
>
> valid[v] = true;
> *wr++ = v;
> for (;;) {
> uint8_t vv = *rd++;
> for (int i = 0; i < n_free; ++i) {
> uint8_t bi = free[i];
> uint8_t ci = b_idx[bi][vv];
> if (ci != BOX_SIZE) {
> result[bi] = ci;
> while (vv != v) {
> bi = db[vv].bi;
> vv = db[vv].parent;
> result[bi] = b_idx[bi][vv];
> };
> return i;
> }
> }
> // add neighbors to database
> for (int bi = 0; bi < N_BOXES; ++bi) {
> if (b_idx[bi][vv] != BOX_SIZE) {
> uint8_t a = bx[bi][result[bi]];
> if (!valid[a]) {
> valid[a] = true;
> db[a] = (db_rec){ .parent = vv, .bi = bi };
> *wr++ = a;
> }
> }
> }
> }
> }
>
> peek_t solver(boxes_t boxes)
> {
> // build index
> uint8_t b_idx[N_BOXES][N_BOXES];
> memset(b_idx, BOX_SIZE, sizeof(b_idx));
> for (int bi = 0; bi < N_BOXES; ++bi) {
> for (int ci = 0; ci < BOX_SIZE; ++ci) {
> uint8_t v = boxes.b[bi][ci];
> if (b_idx[bi][v] == BOX_SIZE)
> b_idx[bi][v] = ci;
> }
> }
>
> uint8_t free_boxes[N_BOXES];
> for (int bi = 0; bi < N_BOXES; ++bi)
> free_boxes[bi] = bi;
> int n_free = N_BOXES;
>
> peek_t result = {0};
> bool used_sorts[N_BOXES]={0};
> while (n_free > 0) {
> int bi = free_boxes[--n_free]; // new set
> result.b[bi] = 0;
> uint8_t v = boxes.b[bi][0];
> used_sorts[v] = true;
> uint8_t pend_que[N_BOXES],
> *pend_wr = pend_que, *pend_rd = pend_que;
> *pend_wr++ = bi;
> while (pend_wr != pend_rd && n_free != 0) {
> int bk = *pend_rd++;
> for (int ci = 0; ci < BOX_SIZE; ++ci) {
> v = boxes.b[bk][ci];
> if (!used_sorts[v]) {
> // new value in set
> uint8_t v_fi = solver_find(
> b_idx, result.b, free_boxes,
> n_free, v, boxes.b);
> uint8_t v_bi = free_boxes[v_fi];
> used_sorts[v] = true;
> *pend_wr++ = v_bi;
> free_boxes[v_fi] = free_boxes[--n_free];
> // remove from free list
> }
> }
> }
> }
> return result;
> }
I think I could eventually understand what this code is doing, and
after that get a sense of how and why it works. In its current
form I think that would take me a fair amount of time. It would
help to have a roadmap, more evocative names, more functional
decomposition, or ideally all three. Please understand, I'm not
asking or suggesting you do anything; my intention is only to
provide feedback that may be of some benefit to you.
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Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-01 16:34 +0300
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-01 10:02 -0400
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-01 17:15 +0300
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-01 10:28 -0400
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-01 17:58 +0300
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-01 15:20 +0100
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-01 17:56 +0300
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-01 19:50 +0100
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-01 15:56 -0400
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-01 23:33 +0100
Re: Cookies in boxes - algorithmic challenge Richard Harnden <richard.nospam@gmail.invalid> - 2026-04-04 07:43 +0100
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-04 11:54 +0100
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-01 15:24 -0400
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-01 17:24 -0400
Re: Cookies in boxes - algorithmic challenge Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2026-04-02 16:25 +0100
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-02 17:10 +0100
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-02 22:19 +0300
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-02 13:03 -0400
Re: Cookies in boxes - algorithmic challenge Richard Harnden <richard.nospam@gmail.invalid> - 2026-04-02 18:52 +0100
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-02 19:50 +0100
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-02 22:24 +0300
Re: Cookies in boxes - algorithmic challenge Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2026-04-02 20:13 +0100
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-02 22:36 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-02 22:14 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-02 22:10 +0300
Re: Cookies in boxes - algorithmic challenge Tristan Wibberley <tristan.wibberley+netnews2@alumni.manchester.ac.uk> - 2026-04-06 22:36 +0100
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-06 15:42 -0700
Re: Cookies in boxes - algorithmic challenge Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-04-06 15:44 -0700
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-04 13:33 -0400
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-04 21:03 +0300
Re: Cookies in boxes - algorithmic challenge DFS <nospam@dfs.com> - 2026-04-04 14:19 -0400
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-04 20:22 +0100
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-04 22:40 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-04 17:08 -0700
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-08 08:42 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-08 22:23 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-09 21:22 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-10 12:23 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-10 22:41 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-10 16:16 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-11 04:27 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-11 22:56 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-11 15:57 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-12 02:15 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-13 02:03 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-13 17:11 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-16 23:52 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-17 14:44 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-17 07:40 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-17 18:30 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-20 00:43 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-21 20:37 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-21 18:22 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-22 12:05 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-15 02:15 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-16 02:57 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-17 17:04 +0300
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-08 23:45 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-09 16:37 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-10 17:02 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-11 03:45 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-09 00:01 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-09 17:07 -0700
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-10 18:06 +0300
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-11 04:31 -0700
Re: Cookies in boxes - algorithmic challenge Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-16 03:22 -0700
Re: Cookies in boxes - algorithmic challenge Bonita Montero <Bonita.Montero@gmail.com> - 2026-04-17 17:58 +0200
Re: Cookies in boxes - algorithmic challenge Bonita Montero <Bonita.Montero@gmail.com> - 2026-04-17 18:08 +0200
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-17 17:47 +0100
Re: Cookies in boxes - algorithmic challenge Bonita Montero <Bonita.Montero@gmail.com> - 2026-04-17 19:24 +0200
Re: Cookies in boxes - algorithmic challenge scott@slp53.sl.home (Scott Lurndal) - 2026-04-17 19:58 +0000
Re: Cookies in boxes - algorithmic challenge Bonita Montero <Bonita.Montero@gmail.com> - 2026-04-18 05:52 +0200
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-18 11:53 +0100
Re: Cookies in boxes - algorithmic challenge Bart <bc@freeuk.com> - 2026-04-18 12:04 +0100
Re: Cookies in boxes - algorithmic challenge Michael S <already5chosen@yahoo.com> - 2026-04-18 20:35 +0300
Re: Cookies in boxes - algorithmic challenge Bonita Montero <Bonita.Montero@gmail.com> - 2026-04-17 19:52 +0200
Re: Cookies in boxes - algorithmic challenge Bonita Montero <Bonita.Montero@gmail.com> - 2026-04-17 20:17 +0200
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