链表的回文结构
链表的回文结构,时间复杂度O(n),空间复杂度O(1)
bool chkPalindrome(ListNode* head) {
if (!head || !head->next) return true;
ListNode *slow = head, *fast = head;
while (fast->next && fast->next->next) {
slow = slow->next;
fast = fast->next->next;
}
ListNode *last = slow->next, *pre = head;
while (last->next) {
ListNode *tmp = last->next;
last->next = tmp->next;
tmp->next = slow->next;
slow->next = tmp;
}
while (slow->next) {
slow = slow->next;
if (pre->val != slow->val) return false;
pre = pre->next;
}
return true;
}