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PalindromeLL.java
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PalindromeLL.java
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// Definition for singly-linked list.
class ListNode {
int val;
ListNode next;
ListNode() {}
ListNode(int val) { this.val = val; }
ListNode(int val, ListNode next) { this.val = val; this.next = next; }
}
public class PalindromeLL{
public boolean isPalindrome(ListNode head) {
if (head == null) return true;
ListNode fast = head;
ListNode slow = head;
ListNode prev = null;
// Find the middle of the list while reversing the first half
while (fast != null && fast.next != null) {
fast = fast.next.next;
// Reverse the first half of the list
ListNode nextNode = slow.next;
slow.next = prev;
prev = slow;
slow = nextNode;
}
// If the length is odd, move slow pointer one step further
if (fast != null) {
slow = slow.next;
}
// Compare the reversed first half with the second half
while (slow != null) {
if (slow.val != prev.val) {
return false;
}
slow = slow.next;
prev = prev.next;
}
return true;
}
}