hello world 输出 olleh dlrow

string s = "Hello World";

        string[] s2 = s.Split(' ');
        for(int j=0;j<s2.Length;j++)
        {
            char[] c = s2[j].ToCharArray();
            int l = s2[j].Length;
            for (int i = 0;i <l/2;i++)
            {
                char t = c[i];
                c[i] = c[l - i - 1];
                c[l - i - 1] = t;
            }
            s2[j] = new string(c);
        }

return string.Join(" ", s2);