Suggestions to improve code

[admkrk]

Hi,
I'm trying to get my brain working again and running through a new (to me) book. One of the exercises is this:

Make a vector holding the ten string values "zero", "one", ... "nine".
Use that in a program that converts a digit to its corresponding spelled-Out
value; e.g., the input 7 gives the output seven. Have the same program,
using the same input loop, convert spelled-out numbers into their
digit form; e.g., the input seven gives the output 7.

Without the includes, this is what I came up with

int main()
{
    vector<string> s_nums(10);
        s_nums[0] = "zero";
        s_nums[1] = "one";
        s_nums[2] = "two";
        s_nums[3] = "three";
        s_nums[4] = "four";
        s_nums[5] = "five";
        s_nums[6] = "six";
        s_nums[7] = "seven";
        s_nums[8] = "eight";
        s_nums[9] = "nine";

    string num = "0";
    int out_num = 0;

    cout << "\t** NUMBER SPELLER **\n\n";
    cout << "Enter a number to be spelled out (0-9)" << "\n"
        << "or spell out a number to print its digit (ctrl+z to end): ";

    while(cin >> num)
    {
        if(num == s_nums[0] || num == "0")
        {
            out_num = 0;
            if(num == "0")
            {
                cout << s_nums[0] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[1] || num == "1")
        {
            out_num = 1;
            if(num == "1")
            {
                cout << s_nums[1] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[2] || num == "2")
        {
            out_num = 2;
            if(num == "2")
            {
                cout << s_nums[2] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[3] || num == "3")
        {
            out_num = 3;
            if(num == "3")
            {
                cout << s_nums[3] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[4] || num == "4")
        {
            out_num = 4;
            if(num == "4")
            {
                cout << s_nums[4] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[5] || num == "5")
        {
            out_num = 5;
            if(num == "5")
            {
                cout << s_nums[5] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[6] || num == "6")
        {
            out_num = 6;
            if(num == "6")
            {
                cout << s_nums[6] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[7] || num == "7")
        {
            out_num = 7;
            if(num == "7")
            {
                cout << s_nums[7] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[8] || num == "8")
        {
            out_num = 8;
            if(num == "8")
            {
                cout << s_nums[8] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
        else if(num == s_nums[9] || num == "9")
        {
            out_num = 9;
            if(num == "9")
            {
                cout << s_nums[9] << '\n';
            }
            else
            {
                cout << out_num << '\n';
            }
        }
    }

    return 0;
}

It works fine, but it seems a bit long winded to me and I can't think of a way to really shorten it. I know I don't really need out_num (I was thinking to use it for the subscript originally), but I will need it for the next step that combines this with a calculator. I'd be glad to hear some suggestions.

[nvrmnd]

You can transform the read digit to int, then pass that in to subscript operator of vector

something like

char digit;
while( cin >> digit ) {
    int n = digit - '0'; // http://www.cplusplus.com/forum/beginner/68260/#msg364068

    if( n < nums.size() ) { // if num entered is between 0 && 9
        std::cout << s_nums[ n ] << " ";
    }
}

[giblit]

You can simplify

    vector<string> s_nums(10);
        s_nums[0] = "zero";
        s_nums[1] = "one";
        s_nums[2] = "two";
        s_nums[3] = "three";
        s_nums[4] = "four";
        s_nums[5] = "five";
        s_nums[6] = "six";
        s_nums[7] = "seven";
        s_nums[8] = "eight";
        s_nums[9] = "nine";

to
vector<string> s_nums = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};

@Nvrmind

char digit;
while( cin >> digit ) {
    int n = digit - '0'; // http://www.cplusplus.com/forum/beginner/68260/#msg364068

    if( n < nums.size() ) { // if num entered is between 0 && 9 

Why not simply read into an int? Though I believe the assignment wants the user to enter

zero, one, two, three, four, five, six, seven, eight, nine, 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9

Then convert accordingly.


Maybe something like this to start:

if(input[0] >= '0' && input[0] <= '9' && input.size() == 1)
{
    std::cout << s_nums[input[0]-'0'] << std::endl;
}

Converting it the other way would be a bit more tricky.

I would suggest using a std::map<std::string, int> instead of a vector. Or even std::map<std::string, std::string> I suppose that way you could go both ways easier.
http://www.cplusplus.com/reference/map/map/

[edit] fixed code tags.

[nvrmnd]

Why not simply read into an int?
idk what i'm thinking when i wrote that :DD

[admkrk]

Thanks guys,

It is a bit tricky having both the numbers and having them spelled out, if it was one or the other it would be simple. I've never use map, but this specifies using a vector so I'm pretty much stuck with that. The next part doesn't specify an output so I won't have to change it to its opposite anymore, just accept either as input. That should simplify it a bit since I can just convert the string to an int and go from there.