如何从结尾 c# 反转字符串 2 个字符和 2 个字符

Question

示例string:

A3148579

预期结果：

798514A3

我试过这段代码：

 public static string Reverse(string s)
 {
     char[] charArray = s.ToCharArray();

     Array.Reverse(charArray);

     return new string(charArray);
 }

实际结果是9758413A

但我想要 798514A3

谢谢大家

Answer 1

You can try below code. This is just to give you a idea and you can update based on the test cases and requirement. Below code works fine for your input which you have mentioned. I have not considered if the length is odd. You can do your research and update logic which will help you to learn and know more.

string input = "A3148579";
            Stack stack = new Stack();
            int count = 0;
            string output = "";

            for (int i = 0; i < input.Length/2; i++)
            {
                stack.Push(input.Substring(count, 2));
                count = count + 2;
            }

            while (stack.Count > 0)
            {
                output += stack.Pop().ToString();
            }

Answer 2

您可以将初始字符串拆分为size = 2 的块（例如，在Substring 的帮助下）；请注意 ToCharArray() 返回 chars 即 size = 1 的块。

让我们概括一下解决方案：现在我们有 size 个块

代码：

using System.Linq;

...

public static string Reverse(string s, int size = 2) {
  if (size < 1)
    throw new ArgumentOutOfRangeException(nameof(size));

  if (string.IsNullOrEmpty(s))
    return s;
  
  int n = s.Length / size + (s.Length % size == 0 ? 0 : 1);

  return string.Concat(Enumerable
    .Range(0, n)
    .Select(i => i < n - 1 ? s.Substring(i * size, size) : s.Substring(i * size))
    .Reverse());
}

演示：

Console.Write(Reverse("A3148579"));

结果：

798514A3

Answer 3

C# Example: Split An Array into Multiple Smaller Arrays

使用 Lambda 表达式扩展 Array 类以包含一个名为 Split 的新方法：

public static class MyArrayExtensions
{
    /// <summary>
    /// Splits an array into several smaller arrays.
    /// </summary>
    /// <typeparam name="T">The type of the array.</typeparam>
    /// <param name="array">The array to split.</param>
    /// <param name="size">The size of the smaller arrays.</param>
    /// <returns>An array containing smaller arrays.</returns>
    public static IEnumerable<IEnumerable<T>> Split<T>(this T[] array, int size)
    {
        for (var i = 0; i < (float)array.Length / size; i++)
        {
            yield return array.Skip(i * size).Take(size);
        }
    }
}

测试新的数组类方法：

[TestMethod]
public void TestSplit2()
{
   string str = "A3148579";

    char[] array1 = new char[str.Length];

    for (int i = 0; i < array1.Length; i++)
    {
        array1[i] = i;
    }


    // Split into smaller arrays of maximal 2 elements
    IEnumerable<IEnumerable<int>> splited = array1.Split<int>(2);
    int j = 0;
    foreach (IEnumerable<int> s in splited){
        j++;
    }
    log.InfoFormat("Splitted in to {0} smaller arrays.", j);
}

最后你只需要反转结果数组（更小）。