有一个字符串，里面有字母，数字和标点，例如"1w4rt,5t7?9u"。要求把里面的字母按原来的顺序倒着排列，别的数字和标点不变，结果应该是"1u4tt,5r7?9w"。这是我面试时，面试人员问的一道问题，大家帮解决下
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- C# code
using System;using System.Text.RegularExpressions;class Demo{ static string ReverseAlpha(string s) { string t = Regex.Replace(s, "[^A-Za-z]", ""); char[] c = s.ToCharArray(); for (int i = 0, j = t.Length - 1; i < c.Length; i++) { if (Char.IsLetter(c[i])) // c[i] >= 'A' && c[i] <= 'Z' || c[i] >= 'a' && c[i] <= 'z' { c[i] = t[j]; j--; } } return new string(c); } static void Main() { string s = "1w4rt,5t7?9u"; Console.WriteLine(s); string t = ReverseAlpha(s); Console.WriteLine(t); }}