PalindromeLinkedList.java

// https://leetcode.com/problems/palindrome-linked-list/
/**
 * Definition for singly-linked list.
 * public class ListNode {
 * int val;
 * ListNode next;
 * ListNode() {}
 * ListNode(int val) { this.val = val; }
 * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
classSolution {
publicbooleanisPalindrome(ListNodehead) {
if(head == null || (head != null && head.next == null)) returntrue;

ListNodeslow = head, fast = head.next, prevFast = head;

while(fast != null && fast.next != null){
slow = slow.next;
prevFast = fast.next;
fast = fast.next.next;
 }

ListNodeprev = null, curr = slow.next, next = null;
slow.next = (fast == null) ? prevFast : fast;
while(curr != null){
next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
 }

ListNodetemp = head;
curr = slow.next;
while(curr != null){
if(temp.val != curr.val) returnfalse;
temp = temp.next;
curr = curr.next;
 }

returntrue;
 }
}