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.

Analyse: Write the sort compare function.

Runtime: 24ms

class Solution {
public:
    string largestNumber(vector<int>& nums) {
        string result;
        if(nums.empty()) return result;
        
        sort(nums.begin(), nums.end(), compare);
        for(int i = 0; i < nums.size(); i++)
            result += to_string(nums[i]);
        
        if(result[0] == '0') return "0";
        return result;
    }
    
    static int compare(int a, int b){
        string s1 = to_string(a) + to_string(b);
        string s2 = to_string(b) + to_string(a);
        return s1 > s2;
    }
};