LeetCode:Largest Number(Greedy)

problem:

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.

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

解决思路：这个属于贪心问题。获得拼接最大的数，里面包含两个数拼接最大的子问题。所以采用逐一拼接。要考虑到特殊情况，首数为0的问题。

问题归结为比较两个字符串拼接问题 s1+s2>s2+s1

class Solution {
public:
    string largestNumber(vector<int>& nums) {
        
        vector<string> strarr;
        
        for(int num:nums)
            strarr.push_back(to_string(num));
        sort(strarr.begin(),strarr.end(),compare);
        
        string result;
        for(string str:strarr)
            result+=str;
            
        if(result[0] == '0' && result.size() > 0) 
            return "0";
            
        return result;
    }

private:
    //自定义比较函数 
    static bool compare(string &s1, string &s2)
    {
        return s1 + s2 > s2 + s1;
    }
};