179. 最大数

bool compare(int a,int b)//int比较
{
    string str1=to_string(a);
    string str2=to_string(b);
    return (str1+str2) > (str2+str1);
}

class Solution 
{
public:
    string largestNumber(vector<int>& numbers) 
    {
        string res;
        if(numbers.empty()) return res;
        sort(numbers.begin(),numbers.end(),compare);
        for(int i=0;i < numbers.size();++i)
        {
            res += to_string(numbers[i]);
        }
        //看最高位是否为'0'
        if(res.front() == '0') return "0";
        return res;
    }
};