题解 | #字符串加解密#

import java.io.*;
import java.util.*;
public class Main{
    public static void main(String[]args){
        Scanner sc=new Scanner(System.in);
        String toEncode=sc.nextLine();
        String toDecode=sc.nextLine();
        
        String encoded = encode(toEncode);
        System.out.println(encoded);
        
        String decoded = decode(toDecode);
        System.out.println(decoded);
    }
    
    private static String encode(String toEncode){
        char[] encoded = new char[toEncode.length()];
        for(int i=0;i<toEncode.length();i++){
            char c=toEncode.charAt(i);
            if(c>='a'&&c<='z'){
                encoded[i]=(char)((c-'a'+1)%26+'A');
            }else if(c>='A'&&c<='Z'){
                encoded[i]=(char)((c-'A'+1)%26+'a');
            }else if(c>='0'&&c<='9'){
                encoded[i]=(char)((c-'0'+1)%10+'0');
            }
        }
        return new String(encoded);
    }
    
    private static String decode(String toDecode){
        char[] decoded = new char[toDecode.length()];
        for(int i=0;i<toDecode.length();i++){
            char c=toDecode.charAt(i);
            // 注意边界
            if(c=='a'){
                decoded[i]='Z';
            }else if(c=='A'){
                decoded[i]='z';
            }else if(c=='0'){
                decoded[i]='9';
            }else if(c>'a'&&c<='z'){
                decoded[i]=(char)((c-'a'-1)%26+'A');
            }else if(c>'A'&&c<='Z'){
                decoded[i]=(char)((c-'A'-1)%26+'a');
            }else if(c>'0'&&c<='9'){
                decoded[i]=(char)((c-'0'-1)%10+'0');
            }
        }
        return new String(decoded);
    }
}