Nekiálltam.

```Tesztelve, működik.```
Ha nem lenne átlátható a kód, pastebin: https://pastebin.com/BKsAETyZ

#include <iostream>
#include <iterator>
#include <set>

using namespace std;

bool numberPalindrome(int);

int main() {
int n;
cin >> n;
int x[n];

set<int, greater<int> > s1;

for(int i = 0; i < n; ++i) {
cin >> x[i];
}

for(int i = 0; i < n; ++i) {
if(numberPalindrome(x[i])> 0) {
s1.insert(x[i]);
}
}

set<int> ::reverse_iterator itr;

for (itr = s1.rbegin(); itr != s1.rend(); itr++) {
cout << *itr<<" ";
}

return 0;
}

bool numberPalindrome(int number) {
int numberInitial, numberInvers = 0;
numberInitial = number;

while(number) {
int c = number % 10;
numberInvers = numberInvers * 10 + c;
number = number / 10;
}

if(numberInitial == numberInvers)
return true;
else
return false;
}