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Palindrome Linked List.cpp
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Palindrome Linked List.cpp
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/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
bool isPalindrome(ListNode* head) {
ListNode *fast = head;
ListNode *slow = head;
while (fast && fast->next) {
fast = fast->next->next;
slow = slow->next;
}
if (fast)
slow = slow->next;
// reverse the last half of the list
ListNode *dummy = slow;
ListNode *last = nullptr;
ListNode *next = nullptr;
while(dummy){
next = dummy->next;
dummy->next = last;
last = dummy;
dummy = next;
}
// compare each half of the list
dummy = last;
while(dummy){
if (dummy->val == head->val){
dummy = dummy->next;
head = head->next;
}
else
return false;
}
return true;
}
};