f1010613 |
1 | /* |
2 | * dsf.c: two small functions to handle a disjoint set forest, |
3 | * which is a data structure useful in any solver which has to |
4 | * worry about avoiding closed loops. |
5 | */ |
6 | |
986cc2de |
7 | #include "puzzles.h" |
8 | |
f1010613 |
9 | int dsf_canonify(int *dsf, int val) |
10 | { |
11 | int v2 = val; |
12 | |
13 | while (dsf[val] != val) |
14 | val = dsf[val]; |
15 | |
16 | while (v2 != val) { |
17 | int tmp = dsf[v2]; |
18 | dsf[v2] = val; |
19 | v2 = tmp; |
20 | } |
21 | |
22 | return val; |
23 | } |
24 | |
25 | void dsf_merge(int *dsf, int v1, int v2) |
26 | { |
27 | v1 = dsf_canonify(dsf, v1); |
28 | v2 = dsf_canonify(dsf, v2); |
29 | dsf[v2] = v1; |
30 | } |