［LeetCode］Linked List Cycle II

/**
* 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) {
while(head != NULL){
if (head->val == INT_MIN) return head;
head->val = INT_MIN;
head = head->next;
}

return nullptr;
}
};