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Linked List Cycle
Linked List Cycle
Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
这道题要用双指针，但我想试一下投机取巧的办法行不行，果然A了
1 /** 2 * Definition for singly-linked list. 3 * class ListNode { 4 * int val; 5 * ListNode next; 6 * ListNode(int x) { 7 * val = x; 8 * next = null; 9 * }10 * }11 */12 public class Solution {13 public boolean hasCycle(ListNode head) {14 if(null == head)15 return false;16 ListNode point = head;17 while(null != point){18 if(point.val != Integer.MIN_VALUE)19 point.val = Integer.MIN_VALUE;20 else21 return true;22 point = point.next;23 } 24 return false;25 }26 }
双指针，一个走一步一个走两步，有环两个一定会相遇
1 /** 2 * Definition for singly-linked list. 3 * class ListNode { 4 * int val; 5 * ListNode next; 6 * ListNode(int x) { 7 * val = x; 8 * next = null; 9 * }10 * }11 */12 public class Solution {13 public boolean hasCycle(ListNode head) {14 if(null == head)15 return false;16 ListNode slow = head;17 ListNode fast = head;18 while(fast != null && fast.next != null){19 slow = slow.next;20 fast = fast.next.next;21 if(slow == fast)22 return true;23 }24 return false;25 }26 }
Linked List Cycle
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