PALIN - wrong answer

Is it possible to somehow see what tests exactly my code does not pass? I’m pretty sure this should be correct, and have tested on my own, in which case I don’t find any wrong results.

#include <stdio.h>
#include <bits/stdc++.h>

using namespace std;

string solve(string str) {
int n = str.size();
string result = str;

for(int i=(n-1)/2;i>=0;i--) {
    result[n - i - 1] = result[i];
}

for(int i=0;i<n;i++) {
    if (result[i] > str[i]) return result;
}

for(int i=(n-1)/2;i>=0;i--) {
    if (result[i] == '9') {
        result[i] = result[n - i - 1] = '0';
    } else {
        result[i] = result[n - i - 1] = result[i] + 1;
        return result;
    }
}

return "1" + string(n - 1, '0') + "1";

}

vector solve(vector &arr) {
int n =arr.size();
vector result;

for(int i=0;i<n;i++) {
    result.push_back(solve(arr[i]));
}

return result;

}

int main() {
int n;
cin>>n;
vector arr(n);
for(int i=0;i<n;i++) cin>>arr[i];

vector<string> result = solve(arr);
for(int i=0;i<n;i++) cout<<result[i]<<endl;

return 0;

}