Question

I have a programming assignment where I need to encrypt a 4 digit int, input by user. I have split the int into four separate values and the encrypt and decrypt functions work. My problem is when I put the four separate ints back together, some numbers encrypt to zero (eg. in:1234 out:0189) and I want to store the output into an int for use with other functions.

Right now I have a half-baked solution that prints 0 first if the first int is 0.

void joinInt(){
    if(int1 == 0) {cout << 0;}
    joined = int1 * 1000;
    joined += int2 * 100;
    joined += int3 * 10;
    joined += int4;
    cout << joined << endl;
    }

My goal is to return joined (with the leading zero) rather than just print it within the function.

Answer 1

An int basically stores leading zeros. The problem that you are running into is that you are not printing the leading zeros that are there.

Another, different approach is to create a function that will accept the four int values along with a string and to then return a string with the numbers.

With this approach you have a helper function with very good cohesion, no side effects, reusable where you need something similar to be done.

For instance:

char *joinedIntString (char *pBuff, int int1, int int2, int int3, int int4)
{
    pBuff[0] = (int1 % 10) + '0';
    pBuff[1] = (int2 % 10) + '0';
    pBuff[2] = (int3 % 10) + '0';
    pBuff[3] = (int4 % 10) + '0';
    pBuff[4] = 0;                    // end of string needed.
    return pBuff;
}

Then in the place where you need to print the value you can just call the function with the arguments and the provided character buffer and then just print the character buffer.

With this approach if you have some unreasonable numbers that end up have more than one leading zero, you will get all of the zeros.

Or you may want to have a function that combines the four ints into a single int and then another function that will print the combined int with leading zeros.

int createJoinedInt (int int1, int int2, int int3, int int4)
{
    return (int1 % 10) * 1000 + (int2 % 10) * 100 + (int 3 % 10) * 10 + (int4 % 10);
}

char *joinedIntString (char *pBuff, int joinedInt)
{
    pBuff[0] = ((joinedInt / 1000) % 10) + '0';
    pBuff[1] = ((joinedInt / 100) % 10) + '0';
    pBuff[2] = ((joinedInt / 10) % 10) + '0';
    pBuff[3] = (joinedInt % 10) + '0';
    pBuff[4] = 0;                    // end of string needed.
    return pBuff;
}