Cattle off network - to prove safety office- arranged in an array smallest number

Title: Enter a positive integer array, the array stitching together all the numbers lined up a number, print out all the numbers can be spliced in the smallest one. 3,32,321 input array} {e.g., print the minimum number of three numbers can be arranged to 321,323.
Ideas:
write a collation, the two figures are translated into strings, and then after comparing different sort order of strings, the output of the smaller one.
Finally, the sorted array in order to splice a good output.

class Solution{
public:
	string PrintMinNumber(vector<int> numbers){
		string ans;
		if (numbers.empty()) return ans;
		sort(numbers.begin(), numbers.end(), cmp);
		for (int i = 0; i < numbers.size(); ++i)
		{
			ans += to_string(numbers[i]);
		}
		return ans;
	}
	 static bool cmp(int a, int b)
	{
		string str1 = to_string(a);
		string str2 = to_string(b);
		return (str1 + str2) < (str2 + str1);
	}
};

The python Solution:
wherein the lstrip () method is used or a specified character string truncated space left.

# -*- coding:utf-8 -*-
from functools import cmp_to_key
class Solution:
    def cmp(self, a, b):
        if a + b > b + a:
            return 1
        if a + b < b + a:
            return -1
        else:
            return 0
    def PrintMinNumber(self, numbers):
        # write code here
        if len(numbers) == 0:
            return ""
        numstr = list(map(str, numbers))
        numstr.sort(key=cmp_to_key(self.cmp))
        return"".join(number).lstrip('0')