如何将邮件转换为密文？

Question

#include <iostream>
using namespace std;

int main()
{
    string message;
    cout << "Ahlan ya user ya habibi." <<endl;

    cout <<"what do you like to do today?" <<endl;
    cout <<"please enter the message:" <<endl;
    getline(cin,message);

    for(int i=0;i<message.size();i++)
    {
        if(string(message[i]==32))
        {
            cout<<char(message[i]);
        }
        else if(string( message[i])>=110)
        {
            int x = int(message[i])-13;
            cout<<char(x);
        }
        else
        {
            int x = string (message[i])+13;
            cout<<char(x);
        }
    }
    return 0;
}

E:\\my programe\\quiz\\main.cpp|20|error: no matching function for call to 'std::__cxx11::basic_string<char>::basic_string(char&)'|

E:\\my programe\\quiz\\main.cpp|20|error: invalid conversion from 'char' to 'const char*' [-fpermissive]|

E:\\my programe\\quiz\\main.cpp|27|error: no matching function for call to 'std::__cxx11::basic_string<char>::basic_string(char&)'|

E:\\my programe\\quiz\\main.cpp|27|error: invalid conversion from 'char' to 'const char*' [-fpermissive]|

Answer 1

std::string::operator[] returns a char& reference. You are trying to construct temporary std::string objects with single char values as input, but std::string does not have any constructors that take only a single char as input. That is why you are getting errors.

Even if you could construct a std::string from a single char , you can't compare a std::string to an integer anyway.

You don't need all of those string() (and char() ) casts at all (BTW, your first string() cast is malformed anyway). char is a numeric type. You can compare a char value directly to an integer, and add/subtract and integer directly to/from a char value to produce a new char value.

Try this instead:

#include <iostream>
using namespace std;

int main()
{
    string message;
    cout << "Ahlan ya user ya habibi." << endl;

    cout << "what do you like to do today?" << endl;
    cout << "please enter the message:" << endl;
    getline(cin, message);

    for(int i = 0; i < message.size(); i++)
    {
        if (message[i] == 32)
        {
            cout << message[i];
        }
        else if (message[i] >= 110)
        {
            char x = message[i] - 13;
            cout << x;
        }
        else
        {
            char x = message[i] + 13;
            cout << x;
        }
    }
    return 0;
}

Live Demo