27 lines
593 B
C++
27 lines
593 B
C++
/**
|
|
* 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) {
|
|
ListNode *p1 = head;
|
|
ListNode *p2 = head;
|
|
while(p2!=nullptr && p2->next!=nullptr){
|
|
// walk one step forward
|
|
p1 = p1->next;
|
|
// walk two steps forward
|
|
p2 = p2->next;
|
|
p2 = p2->next;
|
|
if(p1 == p2){
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
};
|