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palindrome
72 lines (71 loc) · 1.9 KB
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palindrome
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/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* findHalf(ListNode* head){
ListNode* fast = head;
ListNode* slow = head;
while(fast->next!=NULL and fast->next->next!=NULL){
fast = fast->next->next;
slow = slow->next;
}
return slow; //mid pointer
}
ListNode* reverse(ListNode* head){
ListNode* curr = head;
ListNode* prev = NULL;
while(curr!=NULL){
ListNode* temp = curr->next;
curr->next = prev;
prev = curr;
curr = temp;
}
return prev;
}
bool isPalindrome(ListNode* head) {
if(head==nullptr) return true;
ListNode* find = findHalf(head);
ListNode* point = reverse(find->next);
ListNode* p1 = head;
ListNode* p2 = point;
bool res = true;
while(p2!=nullptr){
if(p1->val != p2->val) return false;
p1 = p1->next;
p2 = p2->next;
}
// cout<<point->val;
// find->next =
find->next = reverse(point);
// while(head!=NULL) {
// cout<<head->val;
// head = head->next;
// }
return res;
}
bool isPalindrome1(ListNode* head) {
vector<int> vec;
while(head!=NULL){
vec.push_back(head->val);
head=head->next;
}
int l =0 , r = vec.size()-1,f=1;
while(l<r){
if(vec[l]==vec[r]){
l++,r--;
}
else return false;
}
return true;
// if(head==NULL or head->next==NULL) return true;
// if(head)
}
};