Using char array?

[llfenomeno]

I am completely lost in my progress and have no idea what path to take. I've spend several days searching for ideas online, but I haven't been able to compile my program correctly.

What I need to do is take an assignment list(may include a range) and print back a list of the problems assigned.

Here's an example:

User types in:

L4-5,1-3,7-10,8-12

Computer displays:

Do problems 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, and 12 of L.

The spaces around the input aren't necessary. So L1-3 should result in the same answer as L 1 - 3.

Here's my progress. I am aware that it is a mess; however, it is a result of my lack of understanding of how to go about it.

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

int main()
{
        char problem_set[256];
        cout << "ENTER problem set: ";
        getline(cin, problem_set);
        int i, j, k;
        int l;
        l = sizeof(problem_set);
        cout << l;
        while(i < l)
                for(i = 0;i < l ;i++)
                {
                        string a;//Output string that displays entire problem set.
                        i = j;
                        if(problem_set[j] == isdigit(problem_set[j]))
                                string a = a + problem_set[i];
                                cout << "Do Problems: " << problem_set[i] << " of L";
                        if(problem_set[i] == '-')
                        {
                                digit_after_dash = problem_set[i + 1];
                                digit_before_dash = problem_set[i - 1];
                                for(i = 0; i < l; i++)
                                        range = dbd + ", " + (dbd + i)
                        }
                }

        return 0;
}

[AbstractionAnon]

Line 11: You're using the string version of getline. while problem_set is declared as a char array. If you're going to use a char array, you want

  cin.getline (problem_set, 256);

Or change problem_set to a std::string.

Line 14: You want to use strlen(), not sizeof, unless you change problem_set to std::string, then you want problem_set.size().

Line 16: i is uninitialized. You're going to be testing garbage.

Line 16-17: No need for two loops here. The termination condition of the two loops are the same.

Line 20: Where is j initialized? You're going to be setting your loop variable to garbage. It's not a good idea to change your loop variable inside your loop.

Line 22: You're introducing a new instance of a which is different from the variable declared on line 19.

Line 26: digits_after_dash is undefined.

Line 27: digits_before_dash is undefined.

Line 28: This for loop is going to change your outter loop variable. Are you sure you want to loop l times here?

Line 29: Where is dbd defined? range is undefined.

I don't see that your code handles two digit problem numbers.

Your code doesn't sort the problems. Your input example is out of order, but the example output is ordered.

Also, I don't see you allowing for spaces in the input.

Have you even tried to compile this?

[llfenomeno]

I realize compiling it will get me numerous errors because it is not complete. This was the working progress. I was actually looking for feedback in regards to the approach I am taking. What would be the simplest approach? Another approach I was considering was removing all the commas and spaces, sorting the values numerically, and then adding the commas back in where they belong.

[AbstractionAnon]

I find that compiling as I go along to be a quick way of finding syntax errors early on in the development of a program.

Otherwise, if you wait until the program is complete, you will spend a lot of time fixing syntax errors that could have been caught and fixed earlier when the program was smaller and the errors easier to fix.

As to the approach, I would parse the input field by field, placing numbers in a vector (expanding ranges), then sort the vector and finally print it.

[dhayden]

It looks like the problems must be sorted in the output, so you can't do the output until you read and process all of the input.

I'd use vector<bool> to store whether a specific problem is in the set.
Write a function to addRange(vector<bool> &probs, size_t low, size_t high) to set bits probs[low] through probs[high]. Expand probs if it's too small.
In your parsing code, if you see a N, then call addRange(probs, N, N). If you see M-N then call addRange(M,N);
Finally, iterate over probs and print the result.