Largest Number formed from an Array

problem id:--http://practice.geeksforgeeks.org/problems/largest-number-formed-from-an-array/0

code:--

#include <bits/stdc++.h>

using namespace std;
#define ll   long long
#define      pii               std::pair<int,int>
#define      vi                std::vector<int>
#define      vll               std::vector<long long>
#define      mp(a,b)           make_pair(a,b)
#define      pb(a)             push_back(a)
#define sc(x)   scanf("%d",&x)
#define scll(x)   scanf("%lld",&x)
#define sc2(x,y)   scanf("%d%d",&x,&y)
#define sc3(x,y,z)   scanf("%d%d%d",&x,&y,&z)
#define     pf(x)   printf("%d ",x)
#define     pf2(x,y)   printf("%d %d ",x,y)
#define     pf3(x,y,z)   printf("%d %d %d ",x,y,z)
#define pfnl()   putchar('\n');
#define      each(it,s)        for(auto it = s.begin(); it != s.end(); ++it)
#define      rep(i, n)         for(int i = 0; i < (n); ++i)
#define rep2(i,j,n)   for(int i = j; i < (n); ++i)
#define      fill(a)           memset(a, 0, sizeof (a))
#define      sortA(v)          sort(v.begin(), v.end())
#define      sortD(v)          sort(v.begin(), v.end(), greater<auto>())
#define      X                 first
#define      Y                 second

#define debug(x) cerr<<"debug->"<<#x<<"::"<<x<<endl
#define debug2(x,y) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n"
#define debug3(x,y,z) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\n"
#define MOD 1000000007

bool myfun(int a,int b)  //This function is used to compare two values from the sort function
{
string str1,str2;
str1=to_string(a)+to_string(b);
str2=to_string(b)+to_string(a);
int i=0,j=0;
while(str1[i] && str2[j])
   {
   if(str1[i]==str2[j])
       {++i,++j;continue;}
   else if(str1[i]>str2[j])    return 1;
   else return 0;
   }
return 1;
}

int main(int argc, char **argv) {
//std::ios::sync_with_stdio(false);
int t;
sc(t);
while(t--)
{
int n;
sc(n);
int arr[n];
rep(i,n) sc(arr[i]);
sort(arr,arr+n,myfun);// here we used a functor which is used to sort as per our requirment
rep(i,n) printf("%d",arr[i]);
pfnl();
}
return 0;
}