public:

//compare function

static bool comp (string& s1, string& s2) { return s1+s2 > s2+s1; }

string largestNumber(vector<int> &num) {

//convert int to string

vector<string> v;

for (int i=0; i<num.size(); i++) {

v.push_back(to_string(num[i]));

}

//sort the string

sort(v.begin(), v.end(), comp);

//generate the result

string result;

for(int i=0; i<v.size(); i++ ){

result+=v[i];

}

//special case: start with zero (e.g. [0, 0])

if (result[0]=='0') return "0";

return result;

}