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| #include <iostream>
using namespace std;
struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
//1,2,3,4,3,2,1 1,2,3,3,2,1
class Solution {
public:
int lengthOfList(ListNode* head){
ListNode* p = head;
int count = 0;
while (p!=NULL) {
p = p->next;
count++;
}
return count;
}
ListNode* reveseList(ListNode* head){
ListNode* pre = head;
ListNode* p = head->next;
ListNode* next = NULL;
while (p!=NULL) {
next = p->next;
p->next = pre;
pre = p;
p = next;
}
head->next = NULL;
return pre;
}
bool isPalindrome(ListNode* head) {
if (head==NULL||head->next==NULL) {
return true;
}else{
int len = lengthOfList(head);
int half = len/2;
ListNode* leftStart = head;
ListNode* rightStart = head;
if (len%2!=0) {
half++;
}
for (int i=0; i<half; i++) {
rightStart = rightStart->next;
}
rightStart = reveseList(rightStart);
while (rightStart!=NULL) {
if (leftStart->val==rightStart->val) {
leftStart = leftStart->next;
rightStart = rightStart->next;
}else{
return false;
}
}
return true;
}
}
};
int main(int argc, const char * argv[]) {
return 0;
}
|