Leetcode: Largest Number

Given a list of non negative integers, arrange them such that they form the largest number.

For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.

Note: The result may be very large, so you need to return a string instead of an integer.

class Solution {
public:
static bool cmp(string a, string b) {
	return a + b > b + a;
}
string largestNumber(vector &num) {
	vector snum;
	for (int i = 0; i < num.size(); i++)
		snum.push_back(to_string(num[i]));

	sort(snum.begin(), snum.end(), cmp);

	string res = "";
	for (int i = 0; i < snum.size(); i++)
		res += snum[i];
	
	if (res[0] == '0')
		return "0";
	return res;
}
};