14 bipartite_t *bipartite_new(int n_left, int n_right)
17 bipartite_t *gr = xmalloc(sizeof(*gr) + n_left * sizeof(void *));
18 memset(gr, 0, sizeof(*gr));
21 gr->n_right = n_right;
22 gr->adj = (bitset_t**)(gr + 1);
24 for(i = 0; i < n_left; ++i)
25 gr->adj[i] = bitset_malloc(n_right);
30 void bipartite_free(bipartite_t *gr)
33 for(i = 0; i < gr->n_left; ++i)
34 bitset_free(gr->adj[i]);
38 void bipartite_add(bipartite_t *gr, int i, int j)
40 assert(i < gr->n_left && j < gr->n_right);
41 bitset_set(gr->adj[i], j);
44 void bipartite_remv(bipartite_t *gr, int i, int j)
46 assert(i < gr->n_left && j < gr->n_right);
47 bitset_clear(gr->adj[i], j);
50 int bipartite_adj(const bipartite_t *gr, int i, int j)
52 assert(i < gr->n_left && j < gr->n_right);
53 return bitset_is_set(gr->adj[i], j);
56 static int apply_alternating_path(const bipartite_t *gr, int *matching,
57 bitset_t *matched_left, bitset_t *matched_right)
60 int done_something = 0;
61 bitset_t *tmp = bitset_alloca(gr->n_right);
63 for(left = 0; left < gr->n_left; ++left) {
64 bitset_t *left_adj = gr->adj[left];
67 bitset_copy(tmp, left_adj);
69 if(matching[left] >= 0) {
70 int old_right = matching[left];
72 /* Check of all neighbors of the left node are already matched.
73 * We cannot improve this edge then. */
74 if(bitset_contains(left_adj, matched_right))
77 bitset_andnot(tmp, matched_right);
78 right = bitset_next_set(tmp, 0);
83 We have to find another left node which has the old right one as a neighbor.
84 This node must not be part of a matching
86 for(i = 0; i < gr->n_left; ++i)
87 if(i != left && bitset_is_set(gr->adj[i], old_right) && !bitset_is_set(matched_left, i))
90 /* If no such node can be found, exit. */
94 /* Else, we can improve this edge. */
95 matching[left] = right;
96 matching[i] = old_right;
97 bitset_set(matched_left, i);
98 bitset_set(matched_right, right);
103 /* We have to create a new single edge */
105 assert(!bitset_is_set(matched_left, left));
107 bitset_andnot(tmp, matched_right);
108 if(bitset_popcnt(tmp) == 0)
111 right = bitset_min(tmp);
112 assert(!bitset_is_set(matched_right, right));
113 matching[left] = right;
114 bitset_set(matched_left, left);
115 bitset_set(matched_right, right);
120 return done_something;
123 void bipartite_matching(const bipartite_t *gr, int *matching)
125 bitset_t *matched_left = bitset_alloca(gr->n_left);
126 bitset_t *matched_right = bitset_alloca(gr->n_right);
128 memset(matching, -1, gr->n_left * sizeof(int));
129 while(apply_alternating_path(gr, matching, matched_left, matched_right));
132 void bipartite_dump(FILE *f, const bipartite_t *gr)
136 for(i = 0; i < gr->n_left; ++i) {
137 bitset_fprint(f, gr->adj[i]);