Vigenere密码在保持空间的同时只加密以辅音字母开头的单词[Java]

Question

public class Main {
public static void main(String[] args) {

    Scanner u = new Scanner(System.in);
    final String k = u.next();
    u.nextLine();
    String message = u.nextLine();
    String[] f = message.split(" ");
    System.out.println(encipher(message,k));

    for (String s : f) {
        if (s.charAt(0) == 'a' || s.charAt(0) == 'e' || s.charAt(0) == 'i' ||
                s.charAt(0) == 'o' || s.charAt(0) == 'u') {
            System.out.println(s);
        } else {
            System.out.println(encipher(s, k));
        }

    }
}


public static String encipher(String message, final String key)
{
    String output = "";

    for (int x = 0, y = 0; x < message.length(); x++)
    {
        char c = message.charAt(x);
        if (c < 'a' || c > 'z')
            continue;
        output += (char) ((c + key.charAt(y) - 2 * 'a') % 26 + 'a');
        y = ++y % key.length();
    }

    return output;
}}

Answer 1

当逐字应用加密时，将为每个字重置密钥，并且“de”用“ob”加密：

brasileira
obiobiobio

de
ob

当对整个邮件进行加密时，密钥不会重置(“Olimpiada”有9个字母，可以被“obi”整除。length（）==3)并且“de”用“bi”加密：

olimpiada brasileira de informatica
obiobiobi obiobiobio bi obiobiobiob

因此，如果可能需要记住y索引，或者应该实现另一个方法，在下一个索引的非空键中提供一个字符：

private static Map<String, Integer> keyIndexes = new HashMap<>();

private static char getNextPosition(String key) {
    return key.charAt(keyIndexes.compute(
        key, (k, v) -> v == null ? 0 : (v + 1) % k.length()
    ));
}

private static void resetKey(String key) {
    keyIndexes.remove(key);
}

public static String encipher(String message, final String key)
{
    StringBuilder output = new StringBuilder();

    for (char c : message.toCharArray())
    {
        if (c < 'a' || c > 'z')
            continue; // skip non-letters

        output.append((char) ((c + getNextPosition(key) - 2 * 'a') % 26 + 'a'));
    }

    return output.toString();
}

String message = "olimpiada brasileira de informatica";
String k = "obi";
System.out.println(encipher(message, k));
// !!!
resetKey(k);

for (String s : message.split(" ")) {
    if (s.matches("[aeiou]\\w*")) { // use regexp to detect a word starting with a vowel
        System.out.println(s);
    } else {
        System.out.println(encipher(s, k));
    }
}

cmqaqqoeipsigjtsjzoemwoncsuouqqb   // full message, spaces skipped
olimpiada
psigjtsjzo
em
informatica

public static String encipherWork(String message, final String key) {
    StringBuilder output = new StringBuilder();
    
    boolean inWord = false;
    boolean firstVowel = false;

    for (char c : message.toCharArray()) {
        if ('a' <= c && c <= 'z') {
            if (!inWord) {
                firstVowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
                inWord = true;
            }
            if (!firstVowel) {
                output.append((char) ((c + getNextPosition(key) - 2 * 'a') % 26 + 'a'));
                continue;
            }
        } else {
            inWord = false;
            firstVowel = false;
        }
        output.append(c); // print non-enciphered characters
    }

    return output.toString();
}

olimpiada psigjtsjzo em informatica // full message
olimpiada
psigjtsjzo
em
informatica