字符串加解密

川长思鸟来 2023-07-01 08:58 22阅读 0赞

[https://www.nowcoder.com/practice/2aa32b378a024755a3f251e75cbf233a?tpId=37&tqId=21252&tPage=2&rp=&ru=%2Fta%2Fhuawei&qru=%2Fta%2Fhuawei%2Fquestion-ranking][https_www.nowcoder.com_practice_2aa32b378a024755a3f251e75cbf233a_tpId_37_tqId_21252_tPage_2_rp_ru_2Fta_2Fhuawei_qru_2Fta_2Fhuawei_2Fquestion-ranking]

## 一、题目描述 ##

1、对输入的字符串进行加解密，并输出。

2、加密方法为：

当内容是英文字母时则用该英文字母的后一个字母替换，同时字母变换大小写,如字母a时则替换为B；字母Z时则替换为a；

当内容是数字时则把该数字加1，如0替换1，1替换2，9替换0；

其他字符不做变化。

3、解密方法为加密的逆过程。

## 二、代码实现 ##

取余法：

import java.util.Scanner;
    public class Main {
        
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            
            while (sc.hasNext()) {
                String input1 = sc.next();
                String input2 = sc.next();
                System.out.println(encrypt(input1));
                System.out.println(unEncrypt(input2));
            }
        }
        
        public static String encrypt(String str) {
            StringBuilder sb = new StringBuilder();
            for (int i=0; i<str.length(); i++) {
                char ch = str.charAt(i);
                if (ch>='a' && ch<='z') {
                    sb.append((char)('A'+((ch-'a')+1)%26));
                }
                if (ch>='A' && ch<='Z') {
                    //aucResult[i] = 'a'+((aucPassword[i]-'A')+1)%26;
                    //
                    //aucResult[i] = (char)('a'+((aucPassword[i]-'A')+1)%26);
                    //
                    sb.append((char)('a'+((ch-'A')+1)%26));    //如果没有强转，结果将是错误的
                }
                if (ch>='0' && ch<='9') {
                    //aucResult[i] = '0'+((aucPassword[i]-'0')+1)%10;
                    //
                    //aucResult[i] = (char)('0'+((aucPassword[i]-'0')+1)%10);
                    //
                    sb.append((char)('0'+((ch-'0')+1)%10));
                }
            }
            
            return sb.toString();
        }
        
        public static String unEncrypt(String str) {
            StringBuilder sb = new StringBuilder();
            for (int i=0; i<str.length(); i++) {
                char ch = str.charAt(i);
                if (ch>='a' && ch<='z') {
                    sb.append((char)('A'+((ch-'a')-1+26)%26));
                }
                if (ch>='A' && ch<='Z') {
                    sb.append((char)('a'+((ch-'A')-1+26)%26));
                }
                if (ch>='0' && ch<='9') {
                    sb.append((char)('0'+((ch-'0')-1+10)%10));
                }
            }
            
            return sb.toString();
        }
        
    }

另一种写法：

import java.util.Scanner;
    public class Main {  
        
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            
            while (sc.hasNext()) {
                String input1 = sc.next();
                String input2 = sc.next();
                char[] aucPassword = input1.toCharArray();
                char[] aucResult = new char[aucPassword.length];
                char[] result = input2.toCharArray();
                char[] password = new char[result.length];
                
                encrypt(aucPassword, aucResult);
                for (char item : aucResult) {
                    System.out.print(item);
                }
                System.out.println();
                
                unEncrypt(result, password);
                for (char item : password) {
                    System.out.print(item);
                }
                System.out.println();
                
            }
        }
        
        public static void encrypt(char[] aucPassword, char[] aucResult) {
            for (int i=0; i<aucPassword.length; i++) {
                if (aucPassword[i]>='0' && aucPassword[i]<'9') {
                    aucResult[i] = (char)(aucPassword[i] + 1);
                } else if (aucPassword[i] == '9') {
                    aucResult[i] = '0';
                } else if (aucPassword[i]>='A' && aucPassword[i]<'Z') {
                    aucResult[i] = (char)('a' + aucPassword[i] - 'A' + 1);
                } else if (aucPassword[i] == 'Z') {
                    aucResult[i] = 'a';
                } else if (aucPassword[i]>='a' && aucPassword[i]<'z') {
                    aucResult[i] = (char)('A' + aucPassword[i] - 'a' + 1);
                } else if (aucPassword[i] == 'z') {
                    aucResult[i] = 'A';
                } else {
                    aucResult[i] = aucPassword[i];
                }
            }
        }
        
        public static void unEncrypt(char[] result, char[] password) {
            for (int i=0; i<result.length; i++) {
                if (result[i]>'0' && result[i]<='9') {
                    password[i] = (char)(result[i] - 1);
                } else if (result[i] == '0') {
                    password[i] = '9';
                } else if (result[i]>'A' && result[i]<='Z') {
                    password[i] = (char)('a' + result[i] - 'A' - 1);
                } else if (result[i] == 'A') {
                    password[i] = 'z';
                } else if (result[i]>'a' && result[i]<='z') {
                    password[i] = (char)('A' + result[i] - 'a' - 1);
                } else if (result[i] == 'a') {
                    password[i] = 'Z';
                } else {
                    password[i] = result[i];
                }
            }
        }
        
    }

查表法：

import java.util.Scanner;
    public class Main {
        
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String origin = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
            String trans =  "bcdefghijklmnopqrstuvwxyzaBCDEFGHIJKLMNOPQRSTUVWXYZA1234567890";
            
            while (sc.hasNext()) {
                String input1 = sc.next();
                String input2 = sc.next();
                
                for (int i=0; i<input1.length(); i++) {
                    char ch = input1.charAt(i);
                    int index = origin.indexOf(ch);
                    System.out.print(trans.charAt(index));
                }
                System.out.println();
                
                for (int i=0; i<input2.length(); i++) {
                    char ch = input2.charAt(i);
                    int index = trans.indexOf(ch);
                    System.out.print(origin.charAt(index));
                }
                System.out.println();
            }
        }
       
    }

[https_www.nowcoder.com_practice_2aa32b378a024755a3f251e75cbf233a_tpId_37_tqId_21252_tPage_2_rp_ru_2Fta_2Fhuawei_qru_2Fta_2Fhuawei_2Fquestion-ranking]: https://www.nowcoder.com/practice/2aa32b378a024755a3f251e75cbf233a?tpId=37&tqId=21252&tPage=2&rp=&ru=%2Fta%2Fhuawei&qru=%2Fta%2Fhuawei%2Fquestion-ranking