C\#문자열 자체 감소 알고리즘 상세 설명

/// <summary>
 ///      
 /// </summary>
 public class StringOperation
 {


  /// <summary>
  ///   ASCII  ，      1
  /// </summary>
  /// <param name="pStr">     </param>
  /// <returns></returns>
  public static string StringIncreaseOne(string pStr)
  {
   var vRetStr = pStr;
   if (0 == pStr.Length)
   {
    vRetStr = "1";
   }
   else
   {
    //                 
    string vOtherStr = pStr.Substring(0, pStr.Length - 1);
    int vIntChar = (int)pStr[pStr.Length - 1]; // ASCII  
    if (48 <= vIntChar && vIntChar <= 57) //   （0 - 9）
    {
     vIntChar++; //  1
     if (vIntChar == 58) //    
     {
      vIntChar = 48;
      vOtherStr = StringIncreaseOne(vOtherStr);
     }
    }
    else if (65 <= vIntChar && vIntChar <= 90) //   （A - Z）
    {
     vIntChar++; //  1
     if (vIntChar == 91) 
     {
      vIntChar = 65;
      vOtherStr = StringIncreaseOne(vOtherStr);
     }
    }
    else if (97 <= vIntChar && vIntChar <= 122) //   （a - z）
    {
     vIntChar++; //  1
     if (vIntChar == 123)
     {
      vIntChar = 97;
      vOtherStr = StringIncreaseOne(vOtherStr); 
     }
    }
    else //      ->   
    {
     vOtherStr = StringIncreaseOne(vOtherStr);
    }
    vRetStr = vOtherStr + (char)vIntChar;
   }
   return vRetStr;
  }

  /// <summary>
  ///   ASCII  ，      1
  /// </summary>
  /// <param name="pStr">     </param>
  /// <returns></returns>
  public static string StringReducingOne(string pStr)
  {
   var vRetStr = pStr;
   if (0 == pStr.Length)
   {
    vRetStr = "9";
   }
   else
   {
    string vOtherStr = pStr.Substring(0, pStr.Length - 1);
    int vIntChar = (int)pStr[pStr.Length - 1]; // ASCII  
    if (48 <= vIntChar && vIntChar <= 57) //   （0 - 9）
    {
     vIntChar--;
     if (vIntChar == 47)
     {
      vIntChar = 57;
      vOtherStr = StringReducingOne(vOtherStr);
     }
    }
    else if (65 <= vIntChar && vIntChar <= 90) //   （A - Z）
    {
     vIntChar--; 
     if (vIntChar == 64)
     {
      vIntChar = 90;
      vOtherStr = StringReducingOne(vOtherStr);
     }
    }
    else if (97 <= vIntChar && vIntChar <= 122) //   （a - z）
    {
     vIntChar--;
     if (vIntChar == 96)
     {
      vIntChar = 122;
      vOtherStr = StringReducingOne(vOtherStr);
     }
    }
    else //      ->   
    {
     vOtherStr = StringReducingOne(vOtherStr);
    }
    vRetStr = vOtherStr + (char)vIntChar;
   }
   return vRetStr;
  }

  /// <summary>
  ///   ASCII  ，      
  /// </summary>
  /// <param name="pStr">     </param>
  /// <param name="pCount">    </param>
  /// <returns></returns>
  public static string StringIncrease(string pStr, int pCount)
  {
   string vRetStr = pStr;
   for (int i = 0; i < pCount; i++)
   {
    vRetStr = StringIncreaseOne(vRetStr);
   }
   return vRetStr;
  }

  /// <summary>
  ///   ASCII  ，      
  /// </summary>
  /// <param name="pStr">     </param>
  /// <param name="pCount">    </param>
  /// <returns></returns>
  public static string StringReducing(string pStr, int pCount)
  {
   string vRetStr = pStr;
   for (int i = 0; i < pCount; i++)
   {
    vRetStr = StringReducingOne(vRetStr);
   }   
   return vRetStr;
  }
  


 }