题解 | #字符串加解密#

using System;

class Program {
    public static void Main() {
        // 1 Build maps.
        // 1.1 Build encryption map.
        var enMap = new int[256];
        enMap['z'] = 'A';
        for (var c='a'; c<'z'; ++c) enMap[c] = 'A' + c-'a' + 1;
        enMap['Z'] = 'a';
        for (var c='A'; c<'Z'; ++c) enMap[c] = 'a' + c-'A' + 1;
        enMap['9'] = '0';
        for (var c='0'; c<'9'; ++c) enMap[c] = c + 1;
        // 1.2 Build decryption map.
        var deMap = new int[256];
        deMap['A'] = 'z';
        for (var c='B'; c<='Z'; ++c) deMap[c] = 'a' + c-'A' - 1;
        deMap['a'] = 'Z';
        for (var c='b'; c<='z'; ++c) deMap[c] = 'A' + c-'a' - 1;
        deMap['0'] = '9';
        for (var c='1'; c<='9'; ++c) deMap[c] = c - 1;
        
        // 2 Encrypt and decrypt inputs.
        // 2.1 Encryption.
        for(var ch = Console.Read(); ch!='\n'; ch=Console.Read()) {
            Console.Write((char)enMap[ch]);
        }
        Console.WriteLine();
        // 2.2 Decryption.
        for(var ch = Console.Read(); ch!='\n'; ch=Console.Read()) {
            Console.Write((char)deMap[ch]);
        }
    }
}