179. Largest Number -- 数字字符串比较大小

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 {
    static bool cmp(string s1, string s2) //字符串比较 GOOD！
    {
        return s1+s2 > s2+s1;
    }

public:
    string largestNumber(vector<int>& nums) {
        vector<string> vs;
        for(int i = ; i < nums.size(); i++)
            vs.push_back(to_string(nums[i])); //int转string
        sort(vs.begin(), vs.end(), cmp);
        string s = "";
        for(int i = ; i < vs.size(); i++)
            s += vs[i];
        if(s[] == '')
            return "";
        return s;
    }
};