tsiry-sandratraina.com
A modern Music Player Daemon based on Rockbox open source high quality audio player
libadwaita
audio
rust
zig
deno
mpris
rockbox
mpd
1#include <assert.h>
2#include <string.h>
3
4#include "puzzles.h"
5
6/* horrific and doesn't check overflow. */
7static long factx(long x, long y)
8{
9 long acc = 1, i;
10
11 for (i = y; i <= x; i++)
12 acc *= i;
13 return acc;
14}
15
16void reset_combi(combi_ctx *combi)
17{
18 int i;
19 combi->nleft = combi->total;
20 for (i = 0; i < combi->r; i++)
21 combi->a[i] = i;
22}
23
24combi_ctx *new_combi(int r, int n)
25{
26 long nfr, nrf;
27 combi_ctx *combi;
28
29 assert(r <= n);
30 assert(n >= 1);
31
32 combi = snew(combi_ctx);
33 memset(combi, 0, sizeof(combi_ctx));
34 combi->r = r;
35 combi->n = n;
36
37 combi->a = snewn(r, int);
38 memset(combi->a, 0, r * sizeof(int));
39
40 nfr = factx(n, r+1);
41 nrf = factx(n-r, 1);
42 combi->total = (int)(nfr / nrf);
43
44 reset_combi(combi);
45 return combi;
46}
47
48/* returns NULL when we're done otherwise returns input. */
49combi_ctx *next_combi(combi_ctx *combi)
50{
51 int i = combi->r - 1, j;
52
53 if (combi->nleft == combi->total)
54 goto done;
55 else if (combi->nleft <= 0)
56 return NULL;
57
58 while (combi->a[i] == combi->n - combi->r + i)
59 i--;
60 combi->a[i] += 1;
61 for (j = i+1; j < combi->r; j++)
62 combi->a[j] = combi->a[i] + j - i;
63
64 done:
65 combi->nleft--;
66 return combi;
67}
68
69void free_combi(combi_ctx *combi)
70{
71 sfree(combi->a);
72 sfree(combi);
73}