凯撒密码面向对象编程

Question

我一直在使用面向对象编程实现凯撒密码。问题是，当我调用加密函数时，我得到与用户输入相同的消息...消息未正确加密。

例如，如果我写 "abc" 而不是 "bcd"，我会得到 "abc"。我在 C++ 中尝试过，代码可以正常工作（逻辑很好），但我尝试在 C++ 中使用面向对象的编程并创建了三个文件来分隔代码。

任何人都可以帮助或指出我可能犯的任何错误吗？

可执行测试文件（main 函数）：

#include <iostream>
#include <string>
#include "CyclicShift.h"

using namespace std;


int main()
{

string text;//the string that holds the user input

int key;//key holds the number by which the user wants the alphabets to be     shifted

cout << "Enter your phrase: " << endl;
getline(cin, text);//gets the user input ( including spaces and saves it to the variable text)

cout << "Please choose a number(key) for which you wants the alphabets to be shifted:  " << endl;
/*Note: the key can either be positive (forward shifting), negative (backward shifting) or zero (no shifting)*/

cin >> key;//User input for number by which alphabets are going to be shifted

const CyclicShift aShift;

cout << "Encrypted Message : " << aShift.Encrypt(text, key) << endl;

//system("Pause");

return 0;
}

头文件.h:

#pragma once
#include <iostream>
#include<string>
//Note: No using "namespace std;" in header files 

class CyclicShift
{
private:

char fUpperCase[26];//A-Z
char fLowerCase[26];//a-z

public:
CyclicShift();

std::string& Encrypt(std::string& aOriginalMessage, int &aKey) const;//  Function Prototype.  This declares Encrypt to be a function that needs one string and one integer variables as arguments. Reference operator & in prototype

};

源文件.cpp:

#include "CyclicShift.h"
#include<iostream>
#include<string>

using namespace std;

CyclicShift::CyclicShift()
{
char fUpperCase[26] = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};//Initialization of class member
char fLowerCase[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};//Initialization of class member

}

string& CyclicShift::Encrypt(string& aOriginalMessage, int & aKey) const
{

int z;//z holds the value (int) of the length of the user input ( including spaces)
z = (int)aOriginalMessage.length(); /*give the variable z the value of the user input length and length is normally an unsigned long integer hence
                            we have to typecast it*/

/*counter that makes it keep looping until it "encrypts" all of the user input (that's why it keeps looping while its less than z)*/
for (int i = 0; i < z; i++)
{
    for (int j = 0; j < 26; j++)
    {
        if (aOriginalMessage[i] == fLowerCase[j] || aOriginalMessage[i] == fUpperCase[j])
        {

            if (aKey > 0)
            {
                //another counter that loops forwards key times by incrementing method
                for (int counter = 0; counter < aKey; counter++)
                {
                    /*it checks if the letter text[x] is 'z' and if it is 'z' it will make it 'a'*/
                    if (aOriginalMessage[i] == 'z')
                    {
                        aOriginalMessage[i] = 'a';
                    }

                    else if (aOriginalMessage[i] == 'Z')
                    {
                        aOriginalMessage[i] = 'A';
                    }

                    else
                    {
                        aOriginalMessage[i]++;
                    }

                }
            }

            else    if (aKey < 0)
            {
                //another counter that loops backwards key times by decrementing method
                for (int counter = 0; counter < abs(aKey); counter++)
                {
                    /*it checks if the letter text[x] is 'a' and if it is 'a' it will make it 'z'*/
                    if (aOriginalMessage[i] == 'a')
                    {
                        aOriginalMessage[i] = 'z';
                    }

                    else if (aOriginalMessage[i] == 'A')
                    {
                        aOriginalMessage[i] = 'Z';
                    }

                    else
                    {
                        aOriginalMessage[i]--;
                    }
                }
            }

            else
            {
                aOriginalMessage[i];//No alphabet shifts
            }

        }

        else {

            continue;
            }

        break;
    }

}

return aOriginalMessage;
}

以上是我的面向对象实现的三个代码文件：Testing(main)、Header和source .cpp文件。

Answer 1

对我来说很突出的一个问题是您检查消息的当前字符

if (aOriginalMessage[i] == fLowerCase[j] || aOriginalMessage[i] == fUpperCase[j])

可能在您的轮班更改后。

aOriginalMessage[i]++;

因为您正在遍历所有可能的字符。您可能希望将加密的消息保存在不同的变量中。

另外，先移位整个字母，然后直接为加密消息分配移位的字符可能更有效。

希望对您有所帮助。

Answer 2

下面是我测试过的 C++ 代码，我再次重复它的加密和解密工作....意味着逻辑没问题...

#include<iostream>
#include<string>

using namespace std;

string Encrypt(string&, int &);// Function Prototype.  This declares Encrypt to be a function that needs one variable as string and another as interger as arguments. Reference operator & in prototype
string Decrypt(string&, int &);//Function Prototype.  This declares Decrypt to be a function that needs one variable as string and another as interger as arguments. Reference operator & in prototype

int main()
{

string text;//the string that holds the user input

int key;//key holds the number by which the user wants the alphabets to be shifted

cout << "Enter your phrase: " << endl;
getline(cin, text);//gets the user input ( including spaces and saves it to the variable text)

cout << "Please choose a number(key) for which you wants the alphabets to be shifted:  " << endl;
/*Note: the key can either be positive (forward shifting), negative (backward shifting) or zero (no shifting)*/

cin >> key;//User input for number by which alphabets are going to be shifted

string kolo = Encrypt(text, key);

cout << "Encrypted Message: " << kolo << endl;//Function call to display encrypted message

//Decrypt(Encrypt(text, key), key);

cout << "Decrypted Message: " << Decrypt(kolo, key)<< endl;//Function call to display decrypted message

//system("Pause");

return 0;
}



string Encrypt(string& Source, int& c)
{
char fUpperCase[26] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };//Initialization of class member
char fLowerCase[26] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };//Initialization of class member

int z;//z holds the value (int) of the length of the user input ( including spaces)
z = (int)Source.length();   /*give the variable z the value of the user input length and length is normally an unsigned long integer hence
                            we have to typecast it*/

/*counter that makes it keep looping until it "encrypts" all of the user input (that's why it keeps looping while its less than z)*/
for (int i = 0; i < z; i++)
{
    for (int j = 0; j < 26; j++)
    {
        if (Source[i] == fLowerCase[j] || Source[i] == fUpperCase[j])
        {
            //text[i] = fLowerCase[j];

            if (c > 0)
            {
                //another counter that loops forwards key times by incrementing method
                for (int counter = 0; counter < c; counter++)
                {
                    /*it checks if the letter text[x] is 'z' and if it is 'z' it will make it 'a'*/
                    if (Source[i] == 'z')
                    {
                    Source[i] = 'a';
                    }

                    else if (Source[i] == 'Z')
                    {
                    Source[i] = 'A';
                    }

                    else
                    {
                    Source[i]++;
                    }

                }
            }

            else    if (c < 0)
            {
                //another counter that loops backwards key times by decrementing method
                for (int counter = 0; counter < abs(c); counter++)
                {
                    /*it checks if the letter text[x] is 'a' and if it is 'a' it will make it 'z'*/
                    if (Source[i] == 'a')
                    {
                        Source[i] = 'z';
                    }

                    else if (Source[i] == 'A')
                    {
                        Source[i] = 'Z';
                    }

                    else
                    {
                        Source[i]--;
                    }
                }
            }

            else
            {
                Source[i];//No alphabet shifts
            }

        }

        else {
                continue;
             }

        break;
    }

}

return Source;
}

string Decrypt(string& EncryptedMessage, int& c)
{
int y;//z holds the value (int) of the length of the user input ( including spaces)
y = (int)EncryptedMessage.length(); /*give the variable z the value of the user input length and length is normally an unsigned long integer hence
                            we have to typecast it*/


for (int i = 0; i < y; i++)
{

    if (isalpha(EncryptedMessage[i]))//verify if the all members of the encrypted message is alphabet if not the same special character is return whereas if it is alphabet it is eitther incremented or decremented
    {

        if (c > 0)
        {
            //another counter that loops forwards key times by incrementing method
            for (int counter = 0; counter < c; counter++)
            {
                /*it checks if the letter text[x] is 'a' and if it is 'z' it will make it 'a'*/
                if (EncryptedMessage[i] == 'a')
                {
                    EncryptedMessage[i] = 'z';
                }

                else if (EncryptedMessage[i] == 'A')
                {
                    EncryptedMessage[i] = 'Z';
                }

                else
                {
                    EncryptedMessage[i]--;
                }

            }
        }

        else    if (c < 0)
        {
            //another counter that loops backwards key times by decrementing method
            for (int counter = 0; counter < abs(c); counter++)
            {
                //it checks if the letter text[x] is 'a' and if it is 'a' it will make it 'z'
                if (EncryptedMessage[i] == 'z')
                {
                    EncryptedMessage[i] = 'a';
                }

                else if (EncryptedMessage[i] == 'Z')
                {
                    EncryptedMessage[i] = 'A';
                }

                else
                {
                    EncryptedMessage[i]++;
                }
            }
        }

        else
        {
            EncryptedMessage[i];//No alphabet shifts
        }

    }

    //cout << "Decrypted Message: " << EncryptedMessage << endl;//Function call to display decrypted message


}
return EncryptedMessage;
}

Answer 3

将构造函数代码更改为：

CyclicShift::CyclicShift()
{
    static char const fUpper[26] = { 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z' };//Initialization of class member
    static char const fLower[26] = { 'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z' };//Initialization of class member

    strcpy_s(fUpperCase, fUpper);
    strcpy_s(fLowerCase, fLower);
}

为了避免缓冲区溢出，我将 char 数组的长度更改为 27。

char fUpperCase[27];//A-Z
char fLowerCase[27];//a-z

Answer 4

您应该将fUpperCase和fLowerCase声明为static并在头文件中初始化它们。在您的代码中，您初始化的变量是构造函数的本地变量，而私有成员保持不变。

编辑

如果你必须在构造函数中初始化它们，那么，你可以这样做：

class CyclicShift
{
  private:

    char fUpperCase[26]; // A-Z
    char fLowerCase[26]; // a-z

  // ... etc. ...
}     

CyclicShift::CyclicShift()
{
    for ( int i = 0; i < 26; ++i) {
        fUpperCase[i] = 'A' + i; 
        fLowerCase[i] = 'a' + i;
    }
}

凯撒密码面向对象编程

Caesar cipher object oriented programming

c++

oop

caesar-cipher