179. Largest Number

只需要保证 s1 + s2 > s2 + s1  

class Solution {public:    string largestNumber(vector<int>& nums) {        vector<string> arr;        for(auto i:nums)            arr.push_back(to_string(i));        sort(arr.begin(),arr.end(),compare);        string res;        for(auto s:arr)            res += s;        //考虑全零情况        while(res[0] == '0' && res.length() > 1)            res.erase(0,1);        return res;    }    static bool compare(string &s1,string &s2)    {        return s1 + s2 > s2 + s1;    }};