LeetCode: Linked List Cycle
双指针的简单题
1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * ListNode *next; 6 * ListNode(int x) : val(x), next(NULL) {} 7 * }; 8 */ 9 class Solution { 10 public: 11 bool hasCycle(ListNode *head) { 12 // IMPORTANT: Please reset any member data you declared, as 13 // the same Solution instance will be reused for each test case. 14 if (head == NULL) return false; 15 ListNode *p, *q; 16 p = q = head; 17 while (q) { 18 q = q->next; 19 if (q == NULL) break; 20 if (p == q) return true; 21 p = p->next; 22 q = q->next; 23 } 24 return false; 25 } 26 };
C#
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public int val; 5 * public ListNode next; 6 * public ListNode(int x) { 7 * val = x; 8 * next = null; 9 * } 10 * } 11 */ 12 public class Solution { 13 public bool HasCycle(ListNode head) { 14 if (head == null) return false; 15 ListNode p = head, q = head; 16 while (q != null) { 17 q = q.next; 18 if (q == null) break; 19 if (p == q) return true; 20 p = p.next; 21 q = q.next; 22 } 23 return false; 24 } 25 }