| 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 | |
| 7 | #include "puzzles.h" |
| 8 | |
| 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 | } |