Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
class Solution {
public:
bool hasCycle(ListNode *head) {
ListNode* p1 = head;
ListNode* p2 = head;
while(p1&&p2&&p2->next)
{
p1 = p1->next;
p2 = p2->next->next;
if(p1==p2)
return true;
}
return false;
}
};
