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/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *detectCycle(ListNode *head) {
if(head == NULL){
return NULL;
}
ListNode *fast = head;
ListNode *slow = head;
ListNode *meet = NULL, *p = head;
while(fast && fast->next){
slow = slow->next;
fast = fast->next->next;
if(slow == fast ){
slow = head;
while(fast != slow){
slow = slow->next;
fast = fast->next;
}
return slow;
}
}
return NULL;
}
};
