triangle group

triangle.c

@@ -0,0 +1,61 @@
+#include <stdio.h>
+#include <string.h>
+#include <memory.h>
+
+#include "triangle.h"
+#include "queue.h"
+
+static groupelement_t *find_adj(groupelement_t *cur, int gen, int other, int order)
+{
+	groupelement_t *next = cur->adj[other];
+	for(int i = 0; i < order - 1; i++) {
+		if(!next)
+			break;
+		next = next->adj[gen];
+		if(!next)
+			break;
+		next = next->adj[other];
+	}
+	return next;
+}
+
+int generate_triangle_group(groupelement_t *group, int size, int k1, int k2, int k3)
+{
+	queue_t q;
+	int id, n;
+	groupelement_t *cur;
+
+	int k[3] = {k1, k2, k3};
+
+	memset(group, 0, size*sizeof(groupelement_t));
+	n = 1;
+	queue_init(&q);
+	queue_put(&q, 0);
+
+	while((id = queue_get(&q)) != -1) {
+		cur = &group[id];
+
+		for(int gen = 0; gen < 3; gen++) {
+			if(!cur->adj[gen])
+				cur->adj[gen] = find_adj(cur, gen, (gen+2)%3, k[(gen+1)%3]);
+
+			if(!cur->adj[gen])
+				cur->adj[gen] = find_adj(cur, gen, (gen+1)%3, k[(gen+2)%3]);
+
+			if(!cur->adj[gen] && n < size) {
+				cur->adj[gen] = &group[n];
+				cur->adj[gen]->id = n;
+				cur->adj[gen]->parent = cur;
+				cur->adj[gen]->letter = gen;
+				cur->adj[gen]->length = cur->length + 1;
+				queue_put(&q, n);
+				n++;
+			}
+
+			if(cur->adj[gen])
+				cur->adj[gen]->adj[gen] = cur;
+		}
+	}
+
+	return n;
+}