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44 | public class Solution {
public boolean isPalindrome(ListNode head) {
if (head == null) return true;
ListNode slow = head;
ListNode fast = head;
while (fast.next != null && fast.next.next != null){
fast = fast.next.next;
slow = slow.next;
}
ListNode mid = slow;
slow = slow.next;
ListNode tailHead = reverseList(slow);
ListNode fromBack = tailHead;
ListNode fromFront = head;
boolean result = true;
while (result && fromBack != null){
if (fromBack.val == fromFront.val){
fromBack = fromBack.next;
fromFront = fromFront.next;
}else{
result = false;
}
}
reverseList(tailHead);
return result;
}
ListNode reverseList(ListNode node){
if (node == null || node.next == null) return node;
ListNode current = node.next;
ListNode previous = node;
previous.next = null;
while (current != null){
ListNode next = current.next;
current.next = previous;
previous = current;
current = next;
}
return previous;
}
}
|
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