Wrong ans in form big number

#1

// i can’t understand why it is giving wrong answer please tell me by giving some testcase for which my code // is getting failed

#include
#include
#include
using namespace std;
bool myCompare(string s1,string s2) {
if(s1.compare(s2)>0)
return true;
else
return false;
}

int main() {

int t;
cin >>t;
while(t--) {
    int n;
    cin >>n;
    string s[n];
    for(int i=0;i<n;i++) {
        cin>> s[i];
    }
    sort(s,s+n,myCompare);
    for(int i=0;i<n;i++) {
        cout<< s[i];
    }
    cout<< endl;
}
return 0;

}

#2

@code_dynamo hey ashish your my compare function is not right
try with this compare function
int mycompare(string x, string y)
{
string xy=x.append(y);
string yx=y.append(x);
return xy.compare(yx)>0 ?1 :0;
}