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E234_PalindromeList.java
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E234_PalindromeList.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; }
* }
*/
class Solution {
public boolean isPalindrome(ListNode head) {
ListNode curr = head;
ListNode l = head;
// deep copy list
ListNode rev = new ListNode(0, null);
ListNode dummyHead = rev;
while(l!=null){
rev.next = new ListNode(l.val);
l = l.next;
rev = rev.next;
}
rev = dummyHead.next;
ListNode r = reverseList(rev);
while(r!=null && curr!=null)
{
if(r.val != curr.val)
{
return false;
}
r = r.next;
curr = curr.next;
}
return true;
}
public ListNode reverseList(ListNode l){
ListNode curr = l;
ListNode prev = null;
while(curr!=null){
ListNode temp = curr.next;
curr.next = prev;
prev = curr;
curr = temp;
}
return prev;
}
}