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PalindromeLinkedList.java
54 lines (47 loc) · 1.26 KB
/
PalindromeLinkedList.java
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/**
* 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; }
* }
*/
// https://leetcode.com/problems/palindrome-linked-list/
class Solution {
public boolean isPalindrome(ListNode head) {
ListNode p1 = head, nHead = head, p2 = head, prev = null;
int n = 0;
while (nHead != null) {
nHead = nHead.next;
if (nHead != null) {
nHead = nHead.next;
}
p2 = p2.next;
}
// Reverse from p2
ListNode t = p2;
while (t != null) {
if (prev != null) {
ListNode temp = t.next;
t.next = prev;
prev = t;
t = temp;
} else {
prev = t;
t = t.next;
}
n++;
}
p2 = prev;
while (n-- > 0) {
if (p1.val != p2.val) {
return false;
}
p1 = p1.next;
p2 = p2.next;
}
return true;
}
}