Sample case is working but other test cases failed

#1

Code
#include<bits/stdc++.h>
using namespace std;
bool mycompare(string X, string Y)
{
string XY=X.append(Y);
string YX=Y.append(X);
return XY.compare(YX)>0?1:0;
}
void maximumNumber(vector st)
{
sort(st.begin(),st.end(),mycompare);
for(int i=0;i<st.size();i++)
{
cout<<stoi(st[i]);
}
}
using namespace std;
int main() {
int t;
cin>>t;
while(t–)
{
int m;
vector sp;
cin>>m;
while(m–)
{
int temp;
cin>>temp;
string temp2=to_string(temp);
sp.push_back(temp2);
}
maximumNumber(sp);
}
return 0;
}

#2

Firstly, the numbers can be very large so do not convert it to integers using stoi. Print the output in string format itself.
Also after printing the result of each test case, include an endl.

#3

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