It's just O(N) for "aaaaaaaaaaaaa...aaaaa" case, why do I get TLE?

Thanks.

"""

class Solution {

public:

string shortestPalindrome(string s) {

if (s.empty()) {

return "";

}

```
int i = s.size() - 1;
for (; i >= 0; --i) {
int start = 0, end = i;
bool match = true;
while (start < end) {
if (s[start++] != s[end--]) {
match = false;
break;
}
}
if (match) {
break;
}
}
ostringstream oss;
for (int k = s.size() - 1; k >= i + 1; --k) {
oss << s[k];
}
oss << s;
return oss.str();
}
```

};

"""