😴双指针+反转
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
| class Solution {
public:
bool isPalindrome(ListNode* head) {
if(!head || !head->next) return true;
ListNode* slow = head,
*fast = head,
*pre = nullptr,
*n;
while(fast && fast->next)
{
n = slow;
slow = slow->next;
fast = fast->next->next;
n->next = pre;
pre = n;
}
if(fast)
slow = slow->next;
while(slow && pre) {
if(slow->val != pre->val) {
return false;
}
slow = slow->next;
pre = pre->next;
}
return true;
}
};
|
Accepted
26/26 cases passed (28 ms)
Your runtime beats 42.35 % of cpp submissions
Your memory usage beats 88.19 % of cpp submissions (12.4 MB)
😍stack
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
| class Solution {
public:
bool isPalindrome(ListNode* head) {
stack<int> stk;
int count = 0;
auto h = head;
while(h) {
h = h->next;
++count;
}
bool f = false;
while(head) {
if((stk.size() == count / 2) && (count % 2) && !f) {
// cout << head->val << endl;
head = head->next;
f = true;
continue;
}
int val = head->val;
if(stk.size() && val == stk.top())
stk.pop();
else
stk.push(val);
head = head->next;
}
// cout << stk.size() << endl;
return !stk.size();
}
};
|
Accepted
26/26 cases passed (24 ms)
Your runtime beats 72.11 % of cpp submissions
Your memory usage beats 13.39 % of cpp submissions (13.4 MB)
