［LeetCode］Linked List Cycle

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
bool hasCycle(ListNode *head) {
set<ListNode*> hashMap;

ListNode* cur = head;
while(cur != NULL){
if (!hashMap.insert(cur).second){
return true;
}

cur = cur->next;
}

return false;
}
};