题目描述

给一个链表，若其中包含环，请找出该链表的环的入口结点，否则，输出null

  1. /*
  2.  public class ListNode {
  3.     int val;
  4.     ListNode next = null;
  6.     ListNode(int val) {
  7.         this.val = val;
  8.     }
  9. }
  10. */
  11. public class Solution {
  13.      public ListNode EntryNodeOfLoop(ListNode pHead) {
  14.         if (pHead == null) {
  15.             return pHead;
  16.         }
  17.         ListNode fast = pHead;
  18.         ListNode slow = pHead;
  19.         boolean isExist = false;
  20.         while (slow.next != null && fast.next.next != null) {
  21.             slow = slow.next;
  22.             fast = fast.next.next;
  23.             if (slow == fast) {
  24.                 isExist = true;
  25.                 break;
  26.             }
  27.         }
  28.         if (isExist) {
  29.             slow = pHead;
  30.             while (slow != null && fast != null) {
  31.                 if (slow == fast) {
  32.                     return slow;
  33.                 }
  34.                 slow = slow.next;
  35.                 fast = fast.next;
  36.             }
  37.         }
  38.         return null;
  39.     }
  40. }

引用

https://blog.csdn.net/sinat_35261315/article/details/79205157?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param