find_circle.c

typedef struct list_node
{
	struct list_node *next;
} list_node, *plist;


plist find_circle(plist head)
{
	int count, scount, ncount;
	plist p, sp;

	count = 1;
	p = sp;
	
	scount = count;
	sp = p;

	while(1) {
		ncount = scount * 2;
		while(p != sp && count < ncount) {
			p = p->next;
			count++;
		}
		if(p == sp)
			return p;

		sp = p;
		scount = count;
	}
}