写个仿函数,自定义比较规则,那个放前面更小就把哪个放前面,方便

class Solution {
public:
    struct comp{
        bool operator()(string a,string b){
            return a+b<b+a;
        }
    };
    string PrintMinNumber(vector<int> nums) {
        vector<string> str;
        for (int val : nums) {
            str.push_back(to_string(val));
        }  
        sort(str.begin(), str.end(),comp());
        string ans="";
        for(string s:str)
            ans+=s;
        return ans;
    }
};