Question

所以我正在制作一个替换密码，其中 Encipher 和 Decipher 在由单独的各个函数传递特定参数后由同一函数处理。出于某种原因，它正在加密，但它不会解密我的消息。在我的代码中，'cipherAlphabet' 是从关键字创建的，并与普通字母一起使用来解密/加密，同时还打印到文本文件。然而，解密后的代码与加密代码的输出完全相同，我似乎无法理解为什么。任何想法或想法表示赞赏，谢谢！

static string Cipher(string input, string oldAlphabet, string newAlphabet,
                     string &output)
{
    output = "";
    int inputLen = input.size();

    if (oldAlphabet.size() != newAlphabet.size())
    {
        cout << "New alphabet doesn't match size of original alphabet";
        exit(1);
    }

    for (int i = 0; i < inputLen; ++i)
    {
        int oldCharIndex = oldAlphabet.find(tolower(input[i]));

        if (oldCharIndex >= 0)
            output += isupper(input[i]) ? toupper(newAlphabet[oldCharIndex]) : newAlphabet[oldCharIndex];
        else
            output += input[i];
    }

    return output;
}
static string Encipher(string input, string cipherAlphabet, string &output)
{
    string plainAlphabet = "abcdefghijklmnopqrstuvwxyz";
    return Cipher(input, plainAlphabet, cipherAlphabet, output);
}

static string Decipher(string input, string cipherAlphabet, string &output)
{
    string plainAlphabet = "abcdefghijklmnopqrstuvwxyz";
    return Cipher(input, cipherAlphabet, plainAlphabet, output);
}

string encoder(string key)
{
    string encoded = "";
    // This array represents the
    // 26 letters of alphabets
    bool arr[26] = {0};

    // This loop inserts the keyword
    // at the start of the encoded string
    for (int i = 0; i < key.size(); i++)
    {
        if (key[i] >= 'A' && key[i] <= 'Z')
        {
            // To check whether the character is inserted
            // earlier in the encoded string or not
            if (arr[key[i] - 65] == 0)
            {
                encoded += key[i];
                arr[key[i] - 65] = 1;
            }
        }
        else if (key[i] >= 'a' && key[i] <= 'z')
        {
            if (arr[key[i] - 97] == 0)
            {
                encoded += key[i] - 32;
                arr[key[i] - 97] = 1;
            }
        }
    }

    // This loop inserts the remaining
    // characters in the encoded string.
    for (int i = 0; i < 26; i++)
    {
        if (arr[i] == 0)
        {
            arr[i] = 1;
            encoded += char(i + 65);
        }
    }
    return encoded;
}

string removeDuplicate(string str)
{

    set<char> S, Sd;
    string duplicates = "";
    string reduced = "";

    for (char c : str)
    {
        if (S.insert(c).second)
            reduced += c;
        else if (Sd.insert(c).second)
            duplicates += c;
    }

    int length = duplicates.length();

    for (int i = 0; i < length; i++)
    {
        for (int j = 0; j < str.length(); j++)
        {
            str.erase(std::remove(str.begin(), str.end(), duplicates[i]),
                      str.end());
        }
    }

    return str;
}

int main(int argc, char **argv)
{

    string keyword1;

    if (argc > 2)
    {
        cout << "Invalid input. There should only be 1 input (the keyword)." << endl;
        exit(1);
    }
    else
    {
        keyword1 = argv[1];
    }

    string keyword = removeDuplicate(keyword1);

    ifstream inFile("plaintext.txt");
    ofstream outFile("ciphertext.txt");
    ofstream outFile1("decrypted.txt");

    inFile.open("plaintext.txt");

    std::string content((std::istreambuf_iterator<char>(inFile)),
                        (std::istreambuf_iterator<char>()));

    inFile.close();

    string cipherAlphabet = encoder(keyword);
    string cipherText;
    string plainText;

    outFile << Encipher(content, cipherAlphabet, cipherText);
    outFile.close();

    outFile1 << Decipher(cipherText, cipherAlphabet, plainText);
    outFile1.close();
}

Answer 1

字符串 cipherAlphabet 只包含大写字母。

另一方面，在行中

    int oldCharIndex = oldAlphabet.find(tolower(input[i]));

它正在搜索小写字母或非字母字符。

因此，不会有匹配项。

添加

    if (oldCharIndex < 0) oldCharIndex = oldAlphabet.find(toupper(input[i]));

在搜索大写字母的行之后将解决问题。

函数加密但不会解密

1 个答案: