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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) {
if(head == NULL || head->next == NULL){
return true;
}
ListNode* slow = head;
ListNode* fast = head;
while(fast->next && fast->next->next){
slow = slow->next;
fast = fast->next->next;
}
slow = reverseList(slow->next);
while(slow){
if(head->val != slow->val){
return false;
}
head = head->next;
slow = slow->next;
}
return true;
}
ListNode* reverseList(ListNode* head){
ListNode* pre = NULL;
ListNode* next = NULL;
while(head!=NULL){
next=head->next;
head->next=pre;
pre=head;
head=next;
}
return pre;
}
};