题解 | #字符串加解密#

using System;

namespace HJ29
{
    /// <summary>字符串加解密</summary>
    internal class Program
    {
        static void Main(string[] args)
        {
            var strToEncryption = Console.ReadLine();
            var strToDecryption = Console.ReadLine();

            Console.WriteLine(StringEncryption(strToEncryption));
            Console.WriteLine(StringDecryption(strToDecryption));
        }

        static string StringEncryption(string s)
        {
            char[] chars = s.ToCharArray();
            for (int i = 0; i < chars.Length; i++)
            {
                char c = chars[i];
                if (char.IsLetter(c))
                {
                    if (c == 'Z')
                    {
                        chars[i] = 'a';
                        continue;
                    }
                    if (c == 'z')
                    {
                        chars[i] = 'A';
                        continue;
                    }
                    if (char.IsLower(c))
                    {
                        chars[i] = (char)(char.ToUpper(c) + 1);
                    }
                    else
                    {
                        chars[i] = (char)(char.ToLower(c) + 1);
                    }
                }
                else if (char.IsDigit(c))
                {
                    if (c == '9')
                    {
                        chars[i] = '0';
                    }
                    else
                    {
                        chars[i] = (char)(c + 1);
                    }
                }
            }

            return new string(chars);
        }

        static string StringDecryption(string s)
        {
            char[] chars = s.ToCharArray();
            for (int i = 0; i < chars.Length; i++)
            {
                char c = chars[i];
                if (char.IsLetter(c))
                {
                    if (c == 'A')
                    {
                        chars[i] = 'z';
                        continue;
                    }
                    if (c == 'a')
                    {
                        chars[i] = 'Z';
                        continue;
                    }
                    if (char.IsLower(c))
                    {
                        chars[i] = (char)(char.ToUpper(c) - 1);
                    }
                    else
                    {
                        chars[i] = (char)(char.ToLower(c) - 1);
                    }

                }
                else if (char.IsDigit(c))
                {
                    if (c == '0')
                    {
                        chars[i] = '9';
                    }
                    else
                    {
                        chars[i] = (char)(c - 1);
                    }
                }
            }

            return new string(chars);
        }
    }
}