https://school.programmers.co.kr/learn/courses/30/lessons/120822
using System;
public class Solution {
public string solution(string my_string) {
string answer = "";
char[] charArr = my_string.ToCharArray();
Array.Reverse(charArr);
for(int i=0; i<charArr.Length; i++){
answer += charArr[i];
}
return answer;
}
}